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

int main() {
    char inputString[101];
    char decoded;lkjhgfdMessage[51];
    
    scanf("%s", inputString);
    int len = strlen(inputString);
    int decodeIndex = 0;
    for (int i = 0; i < len; i += 2) {
        char digit1 = inputString[i];
        char digit2 = inputString[i+1];
        int asciiValue = (digit1 - '0') * 10 + (digit2 - '0');
        if ((asciiValue >= 65 && asciiValue <= 90) || (asciiValue >= 97 && asciiValue <= 122)) {
            decodedMessage[decodedIndex++] = (char)asciiValue;
        } else {
            printf("Invalid Input\n");
            return 1;
        }
    }
    decodedMessage[decodedIndex] = '\0';
    printf("%s\n", decodedMessage);
    return 0;
}