n = int(input())
A = list(map(int,input().split())) + [10**10]
ans = 0
last = -1
count = 0
for i,a in enumerate(A):
    if last == -1:
        last = a
        count += 1
        
    else:
        if a == last+1:
            count += 1
        else:
            ans += count*(count-1)//2
            count = 1
    last = a
print(ans)