N = int(input())
A = list(map(int,input().split()))
ans = 0
for i in range(N):
    d = A[i]*2
    ans += 1
    l = i
    r = i
    while True:
        if l-1<0 or r+1>=N:break
        l -= 1
        r += 1
        if A[l]+A[r]==d:
            ans += 1
        else:break
for i in range(N-1):
    d = A[i]+A[i+1]
    ans += 1
    l = i
    r = i+1
    while True:
        if l-1<0 or r+1>=N:break
        l -= 1
        r += 1
        if A[l]+A[r]==d:
            ans += 1
        else:break
print(ans)