#include <iostream>

using namespace std;

int main()
{
  int b=0;
  string reshte ;
  cin >> reshte ;


  for(int i=0;i< reshte.size() ;i++)
  {
      if(!((reshte[i]>='0')&&(reshte[i]<='9')))
      {
          b=1;
      }
  }
  if(b==0)
  {
      int s=0;
      for(int i=0;i<reshte.size();i++)
      {
          s=s*10+(reshte[i]-'0');
      }
      cout<<s;
  }
  else
  {
      cout<<"error";
  }
  return 0;
}