#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int p;

int Count(int n,int x)
{ int res=0;

  while(n>=x)
  { res+=n/x;
    n/=x;}

return res;
}

void Cbin()
{ int l=1,r=5*p+5,mid,x;

 while(l<r)
 { mid=(l+r)/2;

   x=Count(mid,5);

   if (p>x) l=mid+1; else r=mid;
 }

  mid=(l+r)/2;

  x=Count(mid,5);

 if (p>x) mid++;

 x=Count(mid,5);

 if (x==p) g<<mid;
  else g<<"-1";
}

int main()
{ f>>p;

  Cbin();

return 0;
}