C++ :

#include<bits/stdc++.h>
using namespace std;
int main()
{
    string a;
    getline(cin , a);
    for(int i = 0;i < a.size();i++)
    {
    	if(islower(a[i]))
    	{
    		if(a[i] == 'z')
    		{
    			a[i] = 'a';
			}
			else
			{
    			a[i] = a[i] + 1;
    		}
		}
	}
	cout << a;
    return 0;
}

Java :

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String n = sc.nextLine();
        char c;
        for (int i = 0; i < n.length(); i++) {
            c = n.charAt(i);
            if(c >= 'a' && c < 'z') {
                c = (char) (c + 1);
                System.out.print(c);
            }else if(c=='z'){
                c = (char) ('a');
                System.out.print(c);
            }else {
                System.out.print(c);
            }
        }
    }
}