n = int(input())
a = list(map(int, input().split()))
ans = 0
current = 1
for i in range(1, n):
    if a[i] == a[i-1] + 1:
        current += 1
    else:
        ans += current * (current - 1) // 2
        current = 1
ans += current * (current - 1) // 2
print(ans)