function main(input) {
  var a = input[0].split(" ");
  if(a[0]==a[1])console.log(a[2]);
  else if(a[2]==a[1])console.log(a[0]);
  else if(a[0]==a[2])console.log(a[1]);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"))
