#include<stdio.h>
#include<string.h>
int main(){
    char s[105];
    if(scanf("%104s",s)!=1)
    int n=strlen(s);
    if(n%2!=0){
        printf("Invalid Input");
        return 0;
    }
    char o[55];
    int k=0;
    for(int i=0;i<n;i=i+2){
        if(s[i]<'0'||s[i]>'9'||s[i+1]<'0'||s[i+1]>'9'){
            printf("Invalid Input");
            return 0;
        }
        int naruto=(s[i] - '0') * 10 + (s[i+1] - '0');
        if (!((naruto >= 65 && naruto <= 90) || (naruto >= 97 && naruto <= 122))){
            printf("Invalid Input");            
            return 0;
        }
        
        o[k++] = (char)naruto;
     }
o[k] = '\0';
    printf("%s", o);
return 0;
 }
    }
    
}