#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(hasDigi{
        printf("Invalid Input");
    }
    return 0;
}