#include <iostream>
#include <fstream.h>
#include <math.h>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int res(unsigned long n,unsigned long r)
{   r=0;
    while(n)
    { r=r+n/5;
      n/=5;
    }
    return r;
}
int main()
{   const int x=-1;
    unsigned long p,n,r=0;
    f>>p;
    n=5*p;
    r=res(n,r);
    if(r==p)
     g<<n;
     else
      { while(n)
        {n-=5;
         r=res(n,r);
         if(r==p) {g<<n;break;}
         else
          if(r<p)
           {g<<x;break;
           }
        }
      }
    f.close();
    g.close();
    return 0;
}