Fighting Ebola

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Read problems statements in Mandarin Chinese, Russian and Vietnamese as well.
An analysis of the ongoing Ebola outbreak reveals that transmission of the virus occurs in social networks. Usually a social network is represented as an undirected graph G = (V, E), where V denotes the set of nodes and E denotes the set of edges. Each node in the graph is assigned an integer weight for it.
At time t = 0, all the nodes of the graph are vulnerable. Node S of the graph has just been infected by Ebola. At each instant of time t > 0, any vulnerable node v which is connected to some infected node u (i.e. (u, v) ∈ E) also gets infected, unless it was vaccinated at some time t^{'} <= t. A node once infected always remains infected and a vaccinated node can never be infected. Obviously once a node is infected, there is no point of vaccinating it. A node is called saved if it is not infected till the end (at t = infinity, a long time afterwards).
You, being incharge of biggest hospital in the area, have been given the responsibility of vaccinating the nodes of the graph. There are total K units of supply of vaccines in the hosptial. Your target is to vaccinate certain number of nodes using these K units of vaccines. You will start vaccinating the nodes from time t = 1, up to time t = K. Note that you can not vaccinate more than one node a particular time. Also notice that it is better to not skip a vaccination at any time instance between t = 1 to t = K, so we enforce you to vaccinate at least some node at each instant. You can choose to vaccinate a node more than once, but it will be pointless. You can also choose to try to vaccinate an already infected node, but it will also be pointless.
What needs to be optimized?
Your score will be the sum of weights of all the nodes those are not infected (at t = inf, after a long time). You have to maximize value of score.
Input
The first line contains four space separated integers N, M, K and S, denoting the number of nodes, the number of edges,the number of units of the vaccines available and the index of the node at which the Ebola virus starts infecting the social network respectively.
The next line contains N space separated integers w_{i} , each integer specifying the weight of i^{th} node, where 1 ≤ i ≤ N.
Then M lines follow.
The i^{th} of such lines contains two space separated integers x and y representing the edge joining nodes x and y.
Output
Output K space separated integers denoting the indices of the nodes in the order of their vaccination. Note that if you don't have any uninfected node to vaccinate, you can print any dummy node to try to vaccinate.
Constraints
 1 ≤ S ≤ N ≤ 10^{4}
 1 ≤ M ≤ 5*10^{4}
 1 ≤ K ≤ 500
 1 ≤ w_{i} ≤ 10^{3}
 Graph G is connected. It does not have multiedges and self loops.
Example
Input: 15 22 3 1 2 3 1 4 5 3 6 8 2 4 8 1 4 8 9 1 2 1 7 1 12 2 3 2 4 2 5 2 6 3 4 3 9 4 6 5 6 5 8 5 10 6 10 7 8 7 11 8 10 9 14 12 13 12 14 12 15 14 15 Output: 2 14 6
Explanation
The above example is well illustrated through following figures. Infection is represented by red circle and vaccination is represented by green circle. At the end of the process nodes 2, 3, 4, 6, 9 and 14 are saved. The sum of the weights of these nodes is 21. So, the score is 21.
t = 0
t = 1
t = 2
t = 3
Test Case Generation
All the test cases have been divided into broadly 4 groups.
Description of groups of test cases
Each group has 5 test files. All the test files in the group will follow these constraints.
 minN ≤ N ≤ maxN
 minM ≤ M ≤ maxM
 minK ≤ K ≤ maxK
 N, M, K will be choosen uniformly randomly in the above described ranges.
 S will choosen uniformly randomly in the range [1..N].
In one test file, Graph G will be a 4regular graph. Please ignore the constraints on M displayed above in that case. All other constraints will be applicable on G.
In one of the test files, the graph will be a connected biparite graph following the given constraints.
In other remaining three files, the graph will be random connected graphs satisfying the given constraints.
Group 1
 minN = 290 & maxN = 300
 minM = 900 & maxM = 1000
 minK = 35 & maxK = 50
Group 2
 minN = 970 & maxN = 1000
 minM = 9900 & maxM = 10000
 minK = 35 & maxK = 50
Group 3
 minN = 9990 & maxN = 10000
 minM = 35000 & maxM = 40000
 minK = 35 & maxK = 50
Group 4
 minN = 9990 & maxN = 10000
 minM = 35000 & maxM = 40000
 minK = 350 & maxK = 500
During the contest, your submissions will be evaluated on the test files. If you get a nonAC verdict in any of the test files, you will be notified about that. However, if you get an AC verdict, then the score displayed will be only of 20% of the test files. Those 20% of the test files will be 4regular, bipartite and 2 random connected graphs of group 4. After the contest, your submission will be rejudged and score will correspond to all the test files.
Author:  nssprogrammer 
Tester:  xcwgf666 
Editorial  http://discuss.codechef.com/problems/EBOLA 
Tags  aug16, challenge, nssprogrammer, researching 
Date Added:  20042015 
Time Limit:  3 sec 
Source Limit:  50000 Bytes 
Languages:  C, CPP14, JAVA, PYTH, PYTH 3.5, PYPY, CS2, PAS fpc, PAS gpc, RUBY, PHP, GO, NODEJS, HASK, SCALA, D, PERL, FORT, WSPC, ADA, CAML, ICK, BF, ASM, CLPS, PRLG, ICON, SCM qobi, PIKE, ST, NICE, LUA, BASH, NEM, LISP sbcl, LISP clisp, SCM guile, JS, ERL, TCL, PERL6, TEXT, SCM chicken, CLOJ, FS 
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