#include <string>
#include <vector>
#include <list>
#include <cmath>
#include <algorithm>
#include <map>
#include <set>
#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;

class Xylophone {
  public:
    int countKeys(vector <int> keys);
};

int Xylophone::countKeys(vector <int> keys)
{
  return 0;
}