#include <iostream>
#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{int P,nf=1,i=0,nr21,nr51,nr2=0,nr5=0, i1,i2,nrwhile;
 f>>P;
 do{ i++;
    nf=nf*i;
    i1=i;
    i2=i;
        while(i1%2==0){nr2++;
        i1=i1/2; cout<<"a";}
        while(i2%5==0){nr5++;
        i2=i2/5;}
 nr21=nr2;
 nr51=nr5;
                    if(nr2<nr5) nr51=nr2;
                    else if (nr2>nr5) nr21=nr5;
                    if(((nr21*nr51)/2)==P) break;

 if(nr21<=nr51) nrwhile=nr21;
 else nrwhile=nr51;
 }while(nrwhile<P);
 if((nr21)>P) g<<"-1";
 else g<<i<<endl;
}