#include <fstream>
#include <cmath>
using namespace std;
 
ifstream cin("fact.in");
ofstream cout("fact.out");
 
int zeros(int n)
{
    int ans=0;
    while(n)
    {
        ans+=(n/5);
        n/=5;
    }
    return ans;
}

int getBiggestBit(int n) {
	int sol = 1;
	while (n) {
		sol += 1;
		n >>= 1;
	}
	return sol;
}


int main()
{
    int p,n;
    cin>>p;
	if (p == 0) {
		cout << 1 << '\n';
		return 0;
	}
	int sol = 0;
	for (int bit = getBiggestBit(p * 5); bit >= 0; -- bit) {
		if (1LL * sol + (1LL << bit) <= p * 5 and zeros(sol + (1 << bit)) <= p) {
			sol += (1 << bit);
		}
	}
	cout << (sol - sol % 5) << '\n';
    return 0;
}