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