#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
const int INF = 1e+9;
const ll LINF = (ll)pow(10,18);

int main(){
    int n;
    string s;

    cin >> n >> s;

    vector<bool> u(n);
    vector<bool> g(n);

    set<int> m;

    for(int i=0; i<n; i++){
        if(s[i] == 'U') u[i] = 1;
        else if(s[i] == 'G') g[i] = 1;
        else m.insert(i);
    }

    int a,b,x;

    ll ans = 0;

    for(auto s : m){
        x = min(s, n-s-1);

        a = s-1; b = s+1;

        while(x--){
            if(u[a] and g[b]) ans++;
            a--; b++;
        }
    }

    cout << ans << endl;
}