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