#include<fstream>
#include<math.h>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int n;
unsigned long long p;
long nrz1( long c )
{
     long x = 0;
     while( c )
     {
            x += c/5;
            c /= 5;
     }
     return x;
}
int bin(int p)
{
    int lo, hi, mid,nrz;
    lo=1;hi=10000000000LL;
    if(p>0)
    {
    mid=(hi+lo)/2;
    if(nrz1(mid)<p) lo=mid+1;
    if(nrz1(mid)==p) hi=mid-1;
    return n;
    }
    else return 0;
}

int main()
{
    f>>p;
    if(p==0) g<<'0'<<'\n';
    if(!bin(p)) g<<"-1"<<'\n';
    else g<<bin(p)<<'\n';
    f.close();
    g.close();
    return 0;
}