#include <fstream>

using namespace std;
FILE * f;
long long p,i,cop=1,nr;
int main()
{
    f=fopen("factorial.in","r");
    ofstream fout("factorial.out");
    fscanf(f,"%d",&p);
    while(p){
  i+=5;
  cop=i;
  while(cop){
  if(cop%5==0)nr++;
  cop=cop/5;
  }
  p=p-nr;
  nr=0;
    }
    fout<<i;
    fclose(f);
    fout.close();
    return 0;
}