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