function main(input){
    alphabets='abcdefghijklmnopqrstuvwxyz'.split("");
    out = '';

    for(i=0;i<25;i++){
        if(alphabets[i]==input){
            out=alphabets[i+1];
        }
    }

    console.log(out);
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));