#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;
 }