#include <iostream>
using namespace std;
int main(){
    int n;cin>>n;
    int prev = -2;
    long long tmp = 0;
    long long ans = 0;
    for(int i = 0; n > i; i++){
        int x;cin>>x;
        if(x-prev == 1){
            tmp++;
        }else{
            ans += tmp*(tmp-1)/2;
            tmp = 1;
        }
        prev = x;
    }
    ans += tmp*(tmp-1)/2;
    cout << ans << endl;
}