N = int(input())
A = list(map(int, input().split()))

ans = 0
b = 1
for i in range(N-1):
    if A[i] + 1 == A[i+1]:
        b += 1
    else:
        ans += b * (b - 1) // 2
        b = 1

ans += b * (b - 1) // 2

print(ans)