#include<stdio.h>
int hasdigit=0;
void reverse()
{
    char ch;
    if(scanf("%d"&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;
}