CodeChef submission 136803 (C++ 4.3.2) plaintext list. Status: WA, problem SNCK03, contest SNACKDWN. By Daemons (Daemons), 2009-11-21 23:59:11.
#include <iostream>
#include <cstring>
#include <stdio.h>
#include <math.h>
using namespace std;
 
typedef long long int64;
#define MOD 1000000007
 
int64 fac[20001], inv[20001];
 
long long modPow(int a, int p) {
	if (p==0) return 1;
	if (p%2==0) {
		int64 x=modPow(a,p/2);
		return (x*x)%MOD;
	} else {
		return ((int64)a*modPow(a,p-1))%MOD;
	}
}
 
void calcFac() {
	fac[0]=1; inv[0]=1;
	fac[1]=1; inv[1]=1;
	for (long long i=2;i<=20000;i++) {
		fac[i]=(fac[i-1]*i)%MOD;
		inv[i]=modPow(fac[i],MOD-2);
	}
}
 
long long comb(int n, int r) {
	return (((fac[n]*inv[r])%MOD)*inv[n-r])%MOD;
}
 
int N,K;
int k[20001];
long long f[32][20041];
 
 
int main() {
	calcFac();
 
/*	int tests;
	scanf("%d",&tests);
	while (tests-->0) {
		scanf("%d %d",&N,&K);
		for (long long i=1;i<=K;i++) {
			scanf("%d",&k[i-1]);
			--k[i-1];
		}
		memset(f,0,sizeof(f));
		for (long long b=0;b<=N;b++) {
			f[K-1][0] = 1;
			//printf("%d %d = %d\n",1,b,f[1][b]);
		}
		for(int at=K-2;at>=0;--at)
		{
			for(int b=0;b<=N;++b)
			{
				int above = (N-1) - k[at] - b;
				long long ret = 0;
				const int len = k[at+1]-k[at];
				if((at&1) == 0)
				{
					//increasing
					//where is the last number
					for(int end=len;end <= above;++end)//above-skip >= len;++skip)
					{
						ret += f[at+1][b+end-len]*comb(end-1,len-1);
						if(ret >= MOD)
						    ret -= MOD;
					}
				}
				else
				{
					//decreasing
					for(int end=len;end <= b;++end)//above-skip >= len;++skip)
					{
						ret += f[at+1][b-end]*comb(end-1,len-1);
						if(ret >= MOD)
						    ret -= MOD;
					}
				}
				f[at][b] = ret;
			}
		}
		//now we simulate for at==0
		long long out = 0;
		//what's the first number, man?
		for(int i=0;i<N;++i)
		{
			out += f[0][i];
			if(out >= MOD)
			    out -= MOD;
		}
		printf("%lld\n",out);
 
		}*/
    return 0;
}
 
/*
3
4 3
1 3 4
10 6
1 2 5 7 8 10
20000 22
1 3 6 10 14 17 19 21 23 29 30 31 40 50 55 57 60 100 202 245 300 20000
*/