function getLineByParam( param ){
  var ret;
  for ( var i=0; i<param[0].length; i++ ) {
    if ( "\n" == param[0].charAt( i ) ) {
      ret = param[0].slice( 0, i );
      param[0] = param[0].slice( ret.length+1 );
      return ret;
    }
  }
  ret = param[0];
  param[0]="";
  return ret;
}

function Main(input) {
  input = [input];
  var tmp = getLineByParam(input).split(" ");
  var A = parseInt( tmp[0] );
  var B = parseInt( tmp[1] );
  var C = parseInt( tmp[2] );
  if ( A === B ) {
    console.log( C );
  }
  else if ( A === C ) {
    console.log( B );
  }
  else if ( B === C ) {
    console.log( A );
  }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));