#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;
}