function Main(input) {
    var C = input[0];

    var list = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];

    var index = list.findIndex(a => a === C);

    console.log(index !== 25 ? list[index + 1] : list[0]);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8").trim().split(/\n|\s/));