#include<bits/stdc++.h>
using namespace std;

#define int long long

signed main(){
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    int n;
    cin >> n;
    string s;
    cin >> s;
    int out = 0;
    for(int i=n-3; i>=0; i--){
        if(s[i]==s[i+1] && s[i]!=s[i+2]){
            out += (n-2-i);
        }
    }
    cout << out << '\n';
}