function main(arg){

	var A = ['z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','p','q','r','s','t','u','v','w','x','y','z'];
	arg = arg.trim("");
	var a = A.indexOf(arg);

    console.log(A[a+1]);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));
