#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main() 
{
    char str[100];
    scanf("%s", str);
    int  len = strlen(str);
    for(int i=0;i<len;i+=2) {
        int value1 = str[i]-'0';
        int value2 = str[i+1]-'0';
        int value  = value1*10+value2;
        if(value<65 || value>122 || value =96) {
            printf("Invalid Input\n");
            return 0;
        }
        printf("%c",value);
    }
    return 0;
}