#include<iostream>
#include<fstream>
#include<math.h>
using namespace std;
int log(unsigned long y)
{
    unsigned long a=5;
    unsigned int nr=1;
    while(a<y)
    {
        a*=5;
        nr++;
    }nr--;
    return nr;
}
int main ()
{
    int P,N,s,i,nr,d;
    unsigned long a=0,b=1000000,c;
    ifstream x("fact.in");
    x>>P;
    do
    {
        s=0;
        c=(a+b)/2;
        nr=log(c);d=0;
     for(i=i;i<=nr;i++)
     {
          d+=c/pow(5,i);
     }
     if(d<P)
     {
         s=1;
         a=c;
     }
     if(d>P)
     {
         s=1;
         b=c;
     }
     if(d==P)
     s=0;
    }
    while(s!=0);
    ofstream zxx("fact.out");
    if(s==0)
    {zxx<<c;}
    else
    {zxx<<-1;;}
    x.close();
    zxx.close();
    return 0;
}