#include<cstdio>
int zero(int n)
{
	int c=0;
	while(n)
	{
		c+=n/5;
		n/=5;
	}
	return c;
}
int cautbin(int p)
{
	int pas =1 <<30,i;
	for(i=0; pas; pas>>=1)
		if(zero(i+pas)<p)
			i+=pas;
	if(zero(1+i)!=p) return -1;
	return 1+i;
}
int main()
{
	int p;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	printf("%d",cautbin(p));
	return 0;
}