#include <bits/stdc++.h>
using namespace std;
int main() {
  queue<int> left;
  queue<int> right;
  int n;
  cin >> n;
  char x;
  for (int i = 0; i < n; ++i) {
    cin >> x;
    if (x == 'D')
      left.push(i);
    else
      right.push(i);
  }
  while (!left.empty() && !right.empty()) {
    if (left.front() < right.front())
      left.push(left.front() + n);
    else
      right.push(right.front() + n);
    right.pop();
    left.pop();
  }
  if (left.empty())
    cout << 'R';
  else
    cout << 'D';
  return 0;
}
