function Main(input) {
    var data = input.split("\n");
    var first_line = data[0].split(" ");
    var second_line = data[1];

    var a = first_line[0];
    var b = first_line[1];
    var c = first_line[2];

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

    var count0 = 0;
    var count1 = 0;
    var count2 = 0;
    var count3 = 0;
    for (x of first_line) {
        if (x === '0') {
            count0 += 1;
        } else if (x === '1') {
            count1 += 1;
        } else if (x === '2') {
            count2 += 1;
        } else if (x === '3') {
            count3 += 1
        }
    }

    if (count0 === 2 || count1 === 2 || count2 ===2 || count3 ===2) {
        if (count0 === 1){
            console.log(0);
        } else if (count1 ===1) {
            console.log(1);
        } else if (count2 ===1) {
            console.log(2);
        } else {
            console.log(3);
        }
    } else {
        if (count0 === 0){
            console.log(0);
        } else if (count1 ===0) {
            console.log(1);
        } else if (count2 ===0) {
            console.log(2);
        } else {
            console.log(3);
        }
    }
}

// Don't edit this line!
Main(require("fs").readFileSync("/dev/stdin", "utf8"));