#include <stdio.h>
int hasDigit=0;
void reverse(){
    char ch;
    if(scanf("%c",&ch)!=1)
    return;
    if(ch=='\n')
    return;
    if(ch='0'&&ch<='9')
    hasDigit=1;
    
    reverse();
    if(!hasDigit)
    printf("%c",ch);
}
    int main(){
        reverse();
        if(hasDigit){
            printf("Invalid input")
        }
        return 0;
    }