#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define AFFINE_A 0x66
#define AFFINE_B 3

// correct answer: flag{You_found_the_answer!}

int main(){
    const char TRUE_ANS[] = "zpdt""{Pxn_zxndl""_tnf_ddzbff!}";
    char input[100] = { 0 };
    printf("Input your answer: ");
    scanf("%s", input);
    if (strlen(input) != strlen(TRUE_ANS)) {
        printf("Wrong input length!\n");
        return 1;
    }
    for(int i = 0; i <= strlen(input); i++) {
        char input_enc = 0;
        if (input[i] >= 'a' && input[i] <= 'z')
            input_enc = (((input[i] - 'a') * AFFINE_A + AFFINE_B) % 26) + 'a';
        else if (input[i] >= 'A' && input[i] <= 'Z')
            input_enc = (((input[i] - 'A') * AFFINE_A + AFFINE_B) % 26) + 'A';
        else
            input_enc = input[i];
        if (input_enc != TRUE_ANS[i]){
            printf("Wrong answer!\n");
            return 1;
        }
    }
    printf("Congratulations!\n");
    return 0;
}