#include <cstdio>
#include <cstdlib>

#define fr(i, a, b) for(int i=0; i<a; ++i)

int main()
{
	int p, s, n = 0;
	int ketto = 0, ot = 0;
	freopen("fact.in", "r", stdin);
	freopen("fact.out", "w", stdout);
	scanf("%d", &p);

	while (true)
	{
		++n;
		s = n;
		while(s%5==0)
		{
			++ot;
			if (ot==p) break;
			s /= 5;
		}
		if (ot==p) break;
	}

	printf("%d", n);
	return 0;
}