#include <iostream>

using namespace std;

int main()
{
  int n,k;
  int s = 0;
  cin >> n >> k;
  char a[n];
  cin >> a;
  for(int i = 0; i<n; i++){
      if( k < 0 ) break;
          if(a[i] == 'C'){
          k = k-1;
          if(k<0)
          s = s+1;
      }

     }
     cout << s;

    return 0;
}