#include<fstream>
using namespace std;
int main()
{
   int i,p,d=0,c=0;
   ifstream f("fact.in");
   f>>p;f.close();
   for(i=1;min(d,c)!=p;i++)
   {int s=i;
    while(!(s%2)){s/=2;d++;}
    while(!(s%5)){s/=5;c++;}}
   ofstream g("fact.out");
   if(!p)g<<1;
   else g<<i-1;g.close();
}