#include <fstream>
#include <math.h>

using namespace std;
ifstream fin ( "fact.in" ) ;
ofstream fout ( "fact.out" ) ;

int s,x,p;
int check(int x)
{
 int s=0;
     for(int i=5;i<=x;i=i*5)
     s=s+x/i;
        return s;
}

int main()
{
    fin>>p;

int st=1,sol;
int dr=500000000;
while(st<=dr)
{
    int mij=(st+dr)/2;
    int k =check(mij);
    if(k>p)
     dr=mij-1;
     else if ( k < p ) st=mij+1;
     else if ( k == p ){
        sol = mij ;break;
     }



}
while(sol%5!=0)
        sol--;

    fout<<sol;

    return 0;
}