LIM = 32

n, e = map(int, raw_input().strip().split())

# collect graph info
back = [None]*n
end = [True]*n
for i in xrange(e):
    a, b, l, r = map(int, raw_input().strip().split())
    a -= 1; b -= 1; l -= 1; r -= 1
    back[b] = a, l, r
    end[a] = False

def traverse(i):
    ''' yields all nodes from i to 0 '''
    while i:
        yield back[i]
        i, l, r = back[i]


# compute cost[l][r]
cost = [[1<<60]*LIM for l in xrange(LIM)]
for i in xrange(n):
    if not end[i]: continue

    # compute costs for path ending in i.
    cL = [0]*(LIM+1)
    cR = [0]*(LIM+1)
    for curr, l, r in traverse(i):
        cL[l] += 1
        cR[r] += 1

    # compute cLL and cRR
    cLL = [L * v for L, v in enumerate(cL)]
    cRR = [R * v for R, v in enumerate(cR)]

    # cumulate
    for L in xrange(LIM-1,-1,-1):
        cL[L] += cL[L+1]
        cLL[L] += cLL[L+1]
    for R in xrange(1,LIM+1):
        cR[R] += cR[R-1]
        cRR[R] += cRR[R-1]

    # compute cost[l][r] for this path
    for r in xrange(LIM):
        c = -(cRR[r] - r * cR[r]);
        for l in xrange(r+1):
            cost[l][r] = min(cost[l][r], c + cLL[l+1] - l * cL[l+1])

# dynamic programming
best = [0]*(LIM+1)
for r in xrange(LIM):
    best[r+1] = min(best[l] + cost[l][r] for l in xrange(r+1))

print best[LIM]