function main(input) {
  input=input.trim();
  const a = parseInt(input.split(" ")[0], 10);
  const b = parseInt(input.split(" ")[1], 10);
  const c = parseInt(input.split(" ")[2], 10);
  if(a!=b&&a!=c){
    console.log(a);
  }else if(b!=a&&b!=c){
    console.log(b);
  }else{
    console.log(c);
  }
  
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));

