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

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

     }
     if(islower(s[i]))
      {
      if(j>'z')
      {
       j = j - 26 ;
       printf("%c", j);
      }
      else
      {
      printf("%c",j);
      }

      }
    }

}
}

}