import sys
input = sys.stdin.readline
from collections import *

N = int(input())
A = list(map(int, input().split()))
ans = 0
cnt = 0

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

ans += cnt*(cnt+1)//2
print(ans)