#include<stdio.h>

int zerouri(int n)
{
	int nr=0;
	while(n)
	{
		nr+=n/5;
		n/=5;
	}
	return nr;
}	

int caut(int p)
{
	int i,pas=(1<<28);
	for(i=0;pas!=0;pas>>=1)
		if(zerouri(i+pas)<p)
			i+=pas;
	if(zerori(i)!=p)
		return -1;
	return i+1;
}	
int main()
{
	int p;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	printf("%d\n",caut(p));
	return 0;
}