C :

#include <stdio.h> 
#include <string.h> 
	char a[100];
 int main()
 {  
	gets(a);
 	int i,len;
	len=strlen(a);
	for (i=0;i<100;i++)
	{
		if (a[i]<='y'&&a[i]>='a')
		{
			a[i]+=1;
		}
		
		else if (a[i]<='Y'&&a[i]>='A') 
		{
			a[i]+=1;
		}
		else if (a[i]=='Z')
		{
			a[i]='A';
		}
		else if (a[i]=='z')
		{
			a[i]='a';
		}
	
	}
	printf ("%s",a);
 }
 

Python :

def jiami(c):
    if c=='z':
        return 'a'
    elif c=='Z':
        return 'A'
    elif c.isalpha():
        return chr(ord(c)+1)
    else:
        return c
str1=input().strip()
for item in str1:
    print(jiami(item),end="")