#include <bits/stdc++.h>
using namespace std;
char(abc,arc,a);
int main(){
  for(i=0;i<=n;++i)
    cin >> a;
  if(cin=abc){
    cout<<"arc"<<endl;
  }
    if(cin=arc){
      cout<<"abc"<<endl;
    }
  else{
    cout<<"error"<<endl;
  }
}