a, n = list(map(int, input().split()))
score = list(map(int, input().split()))
A = []
Maxscore = [0 for i in range(a)]
for i in range(n):
    A.append(list(map(int, input().split())))

Maxscore[0] = score[0]
for i in range(1, a):
    Ch = []
    for j in A:
        if j[1] == i + 1:
            Ch.append(Maxscore[j[0] - 1])
    if Ch == []:
        Maxscore[i] = score[i]
    else:
        Maxscore[i] = max(max(Ch), 0) + score[i]
print(max(Maxscore))