process.stdin.resume();
process.stdin.setEncoding('utf8');
var input_string = '';

process.stdin.on('data', function (chunk) {
    input_string += chunk;
});
const space_input = function (line) {
    var arr = line.replace(/(^\s+)|(\s+$)/g, "").split(" ");
    for (var i = 0; i < arr.length; ++i) {
        arr[i] = +arr[i];
    }
    return arr;
};
const space_input_char = function (line) {
    var arr = line.replace(/(^\s+)|(\s+$)/g, "").split(" ");
    for (var i = 0; i < arr.length; ++i) {
        arr[i] = arr[i];
    }
    return arr;
};

process.stdin.on('end', function () {
    const lines = input_string.split('\n');
    const abc = space_input(lines[0]);
    if(abc[0]==abc[2]){
        console.log(abc[1])
    }
    if(abc[0]==abc[1]){
        console.log(abc[2])
    }
    if(abc[1]==abc[2]){
        console.log(abc[0])
    }
    
});