#include<iostream>
#include<stdio.h>
#define Nmax 100000000
using namespace std;

void search_number(int low, int high, int nr)
{
	int nr5, putere5 = 5;
	int x = ( low + high ) / 2;

	nr5 = x / 5;

	while(true)
	{
		putere5 *= 5;
		if(x / putere5 == 0)
			break;
		nr5 = nr5 + ( x / putere5 );
	}
	if(nr5 == nr)
	{
		while(x % 5 != 0)
			x--;
		cout << x << endl;
	}
	else if(nr5 < nr)
			search_number((low+high)/2, high, nr);
		else
			search_number(low, (low+high)/2, nr);
}
 
int main()
{
    int P;
	int upper_bound = 100000000;
	int lower_bound = 0;

    freopen("fact.in","r", stdin);
    freopen("fact.out", "w", stdout);
 
    cin >> P;
	if(P == 0)
	{
		cout << '1' << endl;
		return 0;
	}
	search_number(lower_bound, upper_bound, P);
    return 0;
}