(function() {
    'use strict';
 
    var lines = [];
    require('readline').createInterface({
      input: process.stdin,
      output: process.stdout
    }).on('line', function(line) {
      lines.push(line);
    });
    process.stdin.on('end', function() {
      //lines.forEach(function(line) {
        //var tokens = line.split(' ').map(Number);
        //    console.log(tokens[0] + ' ' + tokens[1]);
      //}
      //)
      ;
      
    // ToDo start
      var A = lines[0].split(" ")
      if ( A[0] == A[1]){
        console.log( A[2])
      }else if(A[0] == A[2] ){
        console.log( A[1])
      }else{
        console.log( A[0] )
      }
    // ToDo end

    });

    
})();
  
  