#include <bits/stdc++.h>
using namespace std;
const int INF = 1000000;
int main(){
  int N, X, Y;
  cin >> N >> X >> Y;
  string S;
  cin >> S;
  vector<string> T(1);
  for (int i = 0; i < N; i++){
    if (S[i] == 'S'){
      T.push_back("");
    } else {
      T.back() += S[i];
    }
  }
  int M = T.size();
  if (Y >= M){
    cout << -1 << endl;
  } else {
    vector<vector<int>> a(M + 1, vector<int>(M + 1, 0));
    for (int i = 0; i < M; i++){
      for (int j = i + 1; j <= M; j++){
        for (int k = i; k < j; k++){
          int sz = T[k].size();
          for (int l = 0; l < k; l++){
            if (T[k][l] == 'L'){
              a[i][j]--;
            } else {
              a[i][j]++;
            }
            a[i][j] = max(a[i][j], 0);
          }
        }
      }
    }
    vector<vector<int>> dp(M + 1, vector<int>(Y + 2, -INF));
    for (int i = 0; i < M; i++){
      for (int j = 0; j < Y + 2; j++){
        for (int k = i + 1; k <= M; k++){
          dp[k][j + 1] = max(dp[k][j + 1], dp[i][j] + a[i][k]);
        }
      }
    }
    if (dp[M][Y + 1] < X){
      cout << -1 << endl;
    } else {
      assert(false);
    }
  }
}