#include <stdio.h>

int main(){
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	int n;
	scanf("%d",&n);
	if(n==0){printf("1");return 0;}
	
	int nr=n*10;
	
	int pow5=5;
	int nr5=0;
	
	while(pow5<=nr)
	{
		nr5+=nr/pow5;
		pow5*=5;
	}
	
	while(nr5>n)
	{	int local=nr;
		while(local%5==0){
			nr5--;
			local/=5;
		}
		nr-=5;
	}
	if(nr5<n)
		nr+=5;
	printf("%d",nr);
	return 0;
}