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

    int main(int argc,string argv[]){    

        if(argc==2)  //to make sure there's only one string after ./caesar
        {
        int digit=0,key=0;

            for(int i=0,n=strlen(argv[1]);i<n;i++)
            {
                if(argv[1][i]>='0' && argv[1][i]<='9')
                {
                digit= argv[1][i]-'0';
                key=key*10+digit;
                }

                else{
                    printf("Usage: ./caesar keyn");
                    return 1;
                }

        }

        string text=get_string("plainttext:  ");
        printf("ciphertext: ");


        key=key%26;

        for(int i=0,n=strlen(text);i<n;i++){

            if(islower(text[i]))
            {

            text[i]=text[i]+key;

                if(text[i]>'Z')
                {
                    text[i]=text[i]-26;
                }


                printf("%c",(char)text[i]);




            }

        else if(isupper(text[i]))
            {
                text[i]=text[i]+key;

                if(text[i]>'Z')
                {
                    text[i]=text[i]-26;
                }


                printf("%c",(char)text[i]);
            }

            else
            printf("%c",(char)text[i]);


        }

        printf("n %i",key);




        return 0;

        }







    else{
            printf("Usage: ./caesar keyn");
            return 1;
        }
    }

Design and implement a program, caesar, that encrypts messages using Caesar’s cipher.

• Implement your program in a file called caesar.c in a directory called caesar.
• Your program must accept a single command-line argument, a non-negative integer. Let’s call it
• for the sake of discussion.
• If your program is executed without any command-line arguments or with more than one command-line argument, your program should print an error message of your choice (with printf) and return from main a value of 1 (which tends to signify an error) immediately.
• If any of the characters of the command-line argument is not a decimal digit, your program should print the message Usage: ./caesar key and return from main a value of 1.
• Do not assume that
• will be less than or equal to 26. Your program should work for all non-negative integral values of
• less than
• In other words, you don’t need to worry if your program eventually breaks if the user chooses a value for
• that’s too big or almost too big to fit in an int. (Recall that an int can overflow.) But, even if
• is greater than
• alphabetical characters in your program’s input should remain alphabetical characters in your program’s output. For instance, if
• is
• A should not become even though is
• positions away from A in ASCII, per asciitable.com; A should become B, since B is
• positions away from A, provided you wrap around from Z to A.
• Your program must output plaintext: (with two spaces but without a newline) and then prompt the user for a string of plaintext (using get_string).
• Your program must output ciphertext: (with one space but without a newline) followed by the plaintext’s corresponding ciphertext, with each alphabetical character in the plaintext “rotated” by k positions; non-alphabetical characters should be outputted unchanged.
• Your program must preserve case: capitalized letters, though rotated, must remain capitalized letters; lowercase letters, though rotated, must remain lowercase letters.
• After outputting ciphertext, you should print a newline. Your program should then exit by returning 0 from main.

https://cs50.harvard.edu/x/2024/psets/2/caesar/

this is the link to the problem

basically when I try “world, say hello” as my plaintext and 12 as key it doesn’t act like it should, it gives out random output for w and y. like weird question marks in place of it`