caesar

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

int main(int argc, string argv[]){
int n=0,key=0;
     //sanity check for int
 printf("*");
  printf("\nInput:");
    string input=GetString();
    printf("%s",input);
  if(argc!=2)
    {
       printf("Invalid\n");
   }else

    key=atoi(argv[1]);
    n=strlen(input);
for(int i=0;i<n;i++)
{
  if(isupper(input[i]))
  {
  int convnum=(input[i]-65);
  int cipher=(convnum+key)%26;
  //convert to normal asci again and print
  int asciwrd=cipher+65;
  printf("%c",asciwrd);
  }
  else if(islower(input[i]))
  {
  int convnum=input[i]-97;
  int cipher=(convnum+key)%26;
  int asciwrd=cipher+97;
  printf("%c",asciwrd);
  }
  else
  printf("%i",input[i]);
  printf("\n");
  }
 }