"use strict"
function Main(input) {
  input = input.trim();
  const arr = ['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']
  let ret = 0;
  arr.map((val, index) => {
    if(val === input){
      ret = index + 1;
    }
  })

  console.log(arr[ret]);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));