#include <atcoder/all>
using namespace std;
using ll = long long;

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for(auto &&v:a)cin >> v;
    atcoder::dsu uf(n);
    for(int i = 0; i + 1 < n; i++){
        if(a[i + 1] - a[i] == 1){
            uf.merge(i, i + 1);
        }
    }
    auto G = uf.groups();
    ll ans = 0;
    for(auto &&vec:G){
        ans += (long long)(vec.size()) * (vec.size() - 1) / 2;
    }
    cout << ans << endl;
}