#include <fstream>
#define ll long long
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int nz(int x)
{
    ll s=0;
    while(x>4)
    {
        x/=5;
        s+=x;
    }
    return s;
}
int main()
{
    ll p;
    int k;
    fin>>p;
    if(p==0)
        fout<<"1";
    else
    {
        k=p*5;
        bool ok=0;
        ll z=nz(k);
        while(z!=p)
        {
            k=k-5*(z-p);
            z=nz(k);
            if(z==p)
              ok=1;
        }
        if(ok==0)
            fout<<"-1";
        else
            fout<<k;
    }
    return 0;
}