function Main(input) {
  input = input.split(" ");

  var a = parseInt(input[0], 10);
  var b = parseInt(input[1], 10);
  var c = parseInt(input[2], 10);

  if( a == b ) console.log( c );
  if( b == c ) console.log( a );
  if( a == c ) console.log( b );
 }

 Main(require("fs").readFileSync("/dev/stdin", "utf8"));
