// editor2
#include<stdio.h>
void rev(int *arr,int n){
    int *start = arr;
    int temp;
    int end;
    while(start<end){
        temp = *start;
        *start = *end;
        *end = temp;
        start ++;
        end --;
        }
}

int main(){
    int n;
    scanf("%d",n);
    if(n<0){
        printf("Invalid input");
        return 0;
    }
    
}