a

// div2 easy
import java.util.Arrays;

public class Quorum {
  public int count(int[] arr, int k) {
    Arrays.sort(arr);
    int ans = 0;
    for (int i = 0; i < k; i++) ans += arr[i];
    return ans;
  }
}

// div2 med
public class Quacking {
  public int quack(String s) {
    int[] arr = new int[5];
    for (int i = 0; i < s.length(); i++) {
      int idx = quack.indexOf(s.charAt(i));
      if (arr[(idx+4)%5] > 0) arr[(idx+4)%5] -= 1;
      else if (idx != 0) return -1;
      arr[idx]++;
    }
    for (int i = 0; i < 4; i++) if (arr[i] > 0) return -1;
    return arr[4];
  }
}

// div2 hard
public class Queueing {
  public double probFirst(int len1, int len2, int p1, int p2) {
    double[][] dp = new double[len1+1][len2+1];
    for (int i = 1; i <= len2; i++) dp[0][i] = 1.0;
    double q1 = 1./p1, q2 = 1./p2;
    for (int i = 1; i <= len1; i++) {
      for (int j = 1; j <= len2; j++) {
        dp[i][j] = (dp[i-1][j]*q1*(1-q2) + dp[i][j-1]*(1-q1)*q2
            + dp[i-1][j-1]*q1*q2) / (1 - (1-q1)*(1-q2));
        if (dp[i][j] < 1e-20) dp[i][j] = 0;
      }
    }
    return dp[len1][len2];
  }
}