#include<fstream>
using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

int desc(int n)
{
int nr=0,x,j;
for(int i=2; i<=n; i++)
   {
    x = i;
    while(x % 5 == 0)
         {
          x/=5;
          nr++;
         }
   }
return nr;
}

int main()
{
unsigned long long p,st,dr,mij,cif;

f>>p;

st = 1;
dr = p*p;

while(st <= dr)
     {
      mij = (st+dr)/2;

      cif = desc(mij);
      if(cif == p)
        {
         break;
        }
      else if(cif < p)
         st = mij+1;
      else
         dr = mij-1;

     }
long long nr = (st+dr)/2;
if(p != 0)
  {
   while(nr % 5 != 0)
        nr--;
   g<<nr;
  }
else
   g<<1;
f.close();
g.close();
return 0;
}