#include<stdio.h>
#include<cs50.h>
#include<string.h>
#include<ctype.h>

int main (int argc , string argv[])
{
printf("please give me a key: ");
int k = GetInt();
printf("please enter a text : ");
string s = GetString() ;
 for ( int i = 0 ; i < strlen(s) ; i++ )
  {
   int j =s[i] +  k ;
    if (isalpha(s[i]))
    {
     if (isupper(s[i]))
     {
      j = (j % 26)  ;
      printf("%c" , j + 'A');
     }
     if (islower(s[i]))
     {
      j = (j % 26) + 'a' ;
      printf("%c" , j ) ;
     }
    }

  }
  printf("\n");
}