#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;
}