#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int num,p,i,t,k=0;
int factorial (unsigned long num)
{
 if (num==1)
  return 1;
 return factorial(num-2)*num;
}
int main()
{
  unsigned long n=1000;
    f>>p;
    if(i==1) g<<1;
    for(i=2;i<=n;i++)
    {
    t=factorial(i);
    while(t>0)
    {k++;
    t=t/10;}
    if(k==p)
    {
            g<<i;
    break;
    }
    if(i==n)
    g<<(-1);
    k=0;
}

f.close();
g.close();
return 0;
}