#include <stdio.h>

int main()
{
	int a;
	FILE *fin = fopen("fact.in","rb");
	FILE *fout = fopen("fact.out","wb");

	fscanf(fin,"%d",&a);
	if (a==0)
	{
		fprintf(fout,"%d",1);
	}
	int nr_zero=0;
	int i=0;
	int nr=0;
	while (nr_zero<a)
	{
		nr += 5;
		i++;
		nr_zero++;
		if (i%5==0)
		{
			nr_zero++;
		}
	}
	if (nr_zero!=a)
	{
		fprintf(fout,"%d",-1);
	}
	else {
		fprintf(fout,"%d",nr);
	}
	return 0;
}