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

#define MAX_LEN 101
int main(){
    char input[MAX_LEN];
    fgets(input, MAX_LEN, stdin);
    input[strcspn(int, "\n")] = 0;
    
    intlen = strlen(input);
    if (len % 2 != 0 || len > 100) {
        printf("Invalid Input\n");
        return 0;
    }
    
    char output[MAX_LEN / 2 + 1];
    int idx = 0;
    for (int i = 0; i < len; i += 2) {
        int ascii_val = (input[i] - '0') * 10 + (input[i+1] - '0');
        if (ascii_val < 65 || ascii_val > 90) {
            printf("Invalid Input\n");
            return 0;
        }
        output[idx++] = (char)ascii_val;
    }
    output[idx] = '\0';
    
    printf("%s\n", output);
    return 0;
}