#include <iostream>
using namespace::std;

int write(int nr)
{
	FILE *fout;
	fout = fopen("fact.out","w");
	fprintf(fout,"%d",nr);
	fclose(fout);
	return 0;
}

int main()
{
	FILE *fin;
	int p=0, count, n, total=0, nr, i;
	//long long int n;

	fin = fopen("fact.in", "r");
	fscanf(fin,"%d", &p);
	fclose(fin);

	if(p==0) 
	{
		write(1);
		return 0;
	}

	i=1;
	while(total<p)
	{
		count=1;
		nr=i;
		while(nr%5 == 0)
		{
			count++;
			nr /= 5;
		};
		total += count;

		i++;
	}
		if(total==p) write(5*(i-1)); 
		if(total>p) write(-1); 

	return 0;
}