#include <bits/stdc++.h>
#include<atcoder/all>
#define int long long
#define double long double
using namespace std;
int size(int number){
    string numstr=to_string(number);
    return numstr.size();
}
signed main(void){
    int N;
    cin>>N;
    vector<int>A(N);
    for(int i=0;i<N;++i){
        cin>>A.at(i);
    }
    int cnt=0;
    int ans=0;
    A.push_back(pow(10,9)+200);
    for(int i=1;i<N+1;++i){
        if(A.at(i)==A.at(i-1)+1){
            cnt++;
        }else{
            ans+=cnt*(cnt+1)/2;
            cnt=0;
        }
    }
    cout<<ans<<endl;
}