// editor4
#include<stdio.h>
#include<string.h>
#include<stdlib.h>

int main() {
    char inputString[101];
    scanf("%s", inputString);
    int len = strlen(inputString);
    
    if (len % 2 != 0 || len > 100) {
        printf("Invalid Input\n");
        return 1;
    }
    char decodedMessage[51];
    int decodedIndex = 0;
    
    for (i = 0; i < len; i += 2) {
        char pair[3];
        pair[0] = inputString[i];
        pair[1] = inputString[i+1];
        pair[2] = '\0';
        
         int asciiValue = atoi(pair);
       
        if(asciiValue >= 65 && asciiValue <= 90) {
            decodedMessage[decodedIndex++] = (char)asciiValue;
        } else {
            printf("Invalid Input\n");
            return 1;
        }
    }
    decodedMessage[decodedIndex] = '\0';
    printf("%s\n", decodedMessage);
    return 0;
}