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

void decode_message(const char *input) {
    int len = strlen(input);

    // Check if length is even
    if (len % 2 != 0) {
        printf("Invalid Input\n");
        return;
    }

    for (int i = 0; i < len; i += 2) {
        // Extract pair of digits and convert to integer
        int ascii_value = (input[i] - '0') * 10 + (input[i + 1] - '0');

        // Check if valid alphabet ASCII range (A-Z or a-z)
        if ((ascii_value >= 65 && ascii_value <= 90) || (ascii_value >= 97 && ascii_value <= 122)) {
            printf("%c", ascii_value);
        } else {
            printf("Invalid Input\n");
            return;
        }
    }
    printf("\n");