#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';
}