#include <iostream>
#include <fstream>
using namespace std;
int zerouri(int n)
{
    int p5=5,cnt=0;
    while(n/p5)
    {
        cnt+=n/p5;
        p5*=5;
    }
    return cnt;
}
int main()
{
    ifstream cin ("fact.in");
    ofstream cout ("fact.out");
   int n,st=1,dr,mij,sol;
   cin>>n;
   if(n==0)
      cout<<1;
   dr=2100000000;
   while(st<=dr)
   {
       mij=(st+dr)/2;
       if(zerouri(mij)<n)
       {
           st=mij+1;
       }
       else
       if(zerouri(mij)==n)
       {
           sol=mij;
           dr=mij-1;
       }
       else
       dr=mij-1;
   }
   cout<<sol;
    return 0;
}