#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<algorithm>
#include<vector>
#include<math.h>
#include<iomanip>
#include<stack>
#include<queue>
#include<set>
#include<map>
 
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
 
//const ll mod = 1000000007;
const ll mod = 998244353;
const ld pi = 3.14159265358979;

ll gcd (ll a , ll b) {
	if (a < b) swap(a , b);
	if (b == 0) return 1;
	if (a % b == 0) return b;
	else return gcd (b , a % b);
}

bool is_prime (ll x) {
	if (x == 2 || x == 3 || x == 5 || x == 7) {
		return true;
	}
	for (int i = 3; i * i <= x; i += 2) {
		if(x % i == 0)return false;
	}
	return true;
}

vector<int> divisor (ll x) {
	vector<int> ret;
	for (int i = 2; i * i <= x; i++) {
		while (x % i == 0) {
			ret.push_back(i);
			x /= i;
		}
	}
	if (x > 1) {
		ret.push_back(x);
	}
	return ret;
}

ll modpow (ll x , ll p , ll m) {
	ll ret = 1;
	while (p > 0) {
		if(p % 2 == 1)ret *= x;
		x *= x;
		x %= m;
		p /= 2;
	}
	return ret;
}

void chmax(ll &a , ll &b) {
	if(a < b)a = b;
}

void chmim (ll &a , ll &b) {
	if(a > b)a = b;
}

int main() {	
	cin.tie(0);
	ios::sync_with_stdio(false);
	//cout << fixed << setprecision(15);
	int n;
	cin >> n;
	string s;
	cin >> s;
	vector<int> u;
	int ans = 0;
	for (int i = 0; i < n; i++) {
		if (s[i] == 'U') {
			u.push_back(i);
		}
		if (s[i] == 'M' && u.size() > 0){
			for (int j = 0; j < u.size(); j++) {
				int k = i + i - u[j];
				if (0 <= k && k <= n - 1 && s[k] == 'G') {
					ans += 1;
				}
			}
		}
	} 
	cout << ans << "\n";
	return 0;
}