import sys
input = sys.stdin.readline
from collections import deque
N,M=map(int,input().split())
H=list(map(int,input().split()))
XY=[list(map(lambda x:int(x)-1,input().split())) for _ in range(M)]

edge1 = [[] for _ in range(N)]
edge2 = [[] for _ in range(N)]

ins1 = [0]*N
ins2 = [0]*N

for x,y in XY:
    edge1[x].append((y,max(0, H[y]-H[x])))
    ins1[y]+=1
    edge2[y].append((x,max(0, H[x]-H[y])))
    ins2[x]+=1
INF=10**60
def solve(edge, ins, start, goal):
    dp = [-INF]*N
    dp2 = [-INF]*N
    dp[start]=0

    que = deque()
    for i,j in enumerate(ins):
        if j==0:
            que.append(i)
    while que:
        cur = que.popleft()
        u = dp[cur]
        u2 = dp2[cur]
        for to,h in edge[cur]:
            if h>0:
                dp2[to] = max(dp2[to], u + h)
            else:
                dp[to] = max(dp[to], u2, u)
            ins[to]-=1
            if ins[to]==0:
                que.append(to)
    ans = max(dp[goal], dp2[goal])
    if ans<0:
        print(-1)
    else:
        print(ans)
    # print(dp)
    # print(dp2)

solve(edge1,ins1, 0, -1)
solve(edge2,ins2, -1, 0)