#include<fstream>
using namespace std;
ifstream in;
ofstream out;
long long p,t=0,rasp=0;
int factxiny(int x,int y){
	int p=0;
	while(y%x==0)
	{
		p++;
		y=y/x;
	}
	return p;
}
int main(){
	int player_unu=0;
	in.open("fact.in");
	out.open("fact.out");
	in>>p;
	if(p==0)
		out<<1;
	else
	{
	for(int i=5;i<=100000;i=i+5)
	{
		t=t+factxiny(5,i);
		if(t>=p)
		{
			rasp=i;
			break;
		}
	}
	out<<rasp;}
	in.close();
	out.close();
	return player_unu;
}