#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

#define rep(i, a, b) for (int i = (a); i < (b); ++i)
#define MOD 1000000007
#define int long long
using ll = long long;
using namespace std;
const int INF = 1LL << 50;
using P       = pair<int, int>;

struct Setup {
    Setup() {
        cin.tie(0);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(20);
    }
} SETUP;

template <class T>
bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    } else {
        return false;
    }
}

template <class T>
bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    } else {
        return false;
    }
}

signed main() {
    int len;cin>>len;
    string s;
    cin >> s;
    int ans = 0;
    rep(i, 0, len) {
        if (s[i] == 'U') {
            rep(j, i + 1, len) {
                if (s[j] == 'M') {
                    int k = j + j - i;
                    if (k >= len) break;
                    if (s[k] == 'G') {
                        ans++;
                    }
                }
            }
        }
    }
    cout << ans << endl;
}