#include<stdio.h>
nint hasDigit=0;
void reverse(){
    char ch;
    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;
}