#include <bits/stdc++.h>
using namespace std;

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int si, sj;
  cin >> si >> sj;
  string s;
  cin >> s;
  if (count(begin(s), end(s), 'U') < si or count(begin(s), end(s), 'L') < sj) {
    cout << "-1\n";
    exit(0);
  }
  assert(false);
}