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

int main() {
  int S ;
  cin >> S >> endl;
  if( S == B ){
  cout << A << R << C << endl; 
  }
  if else(S == R ){
  cout << A << B << C << endl;
  }
  else {
  cout << "error" << endl;
  }
  }