#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int zero(int n)
{
    int p=5,nr=0;
    while(n/p>0){nr+=n/p; p*=5;}
    return nr;
}

int cbin(int p)
{
    int l=1,r=(1<<31)-1,m;
    while(l<r)
    {
        m=((long long)l+r)/2;
        if(zero(m)>=p)r=m; else l=m+1;
    }
        if(zero(r)==p)return r;
        return -1;
}

int main()
{
    int p;
   
	f>>p;
	g<<cbin(p)<<endl;
	f.close();
	g.close();
    return 0;
}