#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n >> s;
  queue<int> q;
  int cntD = 0, cntR = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'R')
      cntR++;
    else
      cntD++;
    q.push(i);
  }
  int removeD = 0, removeR = 0;
  while (!q.empty()) {
    if (cntD - removeD <= 0) {
      cout << "R";
      return 0;
    }
    if (cntR - removeR <= 0) {
      cout << "D";
      return 0;
    }
    int top = q.front();
    q.pop();
    if (s[top] == 'R') {
      if (removeR) {
        removeR--;
        cntR--;
      } else {
        removeD++;
        q.push(top);
      }
    } else {
      if (removeD) {
        removeD--;
        cntD--;
      } else {
        removeR++;
        q.push(top);
      }
    }
  }
  return 0;
}
