#include<cstdio>
using namespace std;
int p;
int st=1, dr=2000000000;
int putere(int a)
{
	int c=0;
	for(int i=5;i<=a;i*=5) c+=a/i;
	return c;
}
int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	if(p==0) {printf("1"); return 0;}
	while(st<dr)
	{
		int mij=(st+dr)/2;
        int n=putere(mij);
        if(p<=n) dr=mij;
        else st=mij+1;
	}
	if(putere(st)==p) printf("%d",st);
    else printf("-1");
    return 0;
}