fn main(){
  let n: usize = read();
  let s: String = read();
  let sv: Vec<char> = s.chars().collect();
  let mut ans: usize = 0;
  
  for j in 1 .. n - 1 {
    if sv[j] == 'M' {
      let mut i = j - 1;
      let mut k = j + 1;
      loop {
        if sv[i] == 'U' && sv[k] == 'G' {
          ans += 1;
        }
        if i == 0 || k == n-1 { break; }
        i -= 1;
        k += 1;
      }
    }
  }

  println!("{}", ans);
}

fn read<T>() -> T
  where T: std::str::FromStr,
        T::Err: std::fmt::Debug
{
  let mut buf = String::new();
  std::io::stdin().read_line(&mut buf).expect("failed to read");
  buf.trim().parse().unwrap()
}