#include<iostream>
#include<cmath>
#include<climits>
#include<fstream>

using namespace std;

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

int main () {
    long long i,p,k=0,x;
    fin >> p;
    if(p==0)fout<<"1";

    for (i=1;k<=p;i=i++){
               k++;
               x=i;
               while(x%5==0){x=x/5;
                                         k++;}
    }
    fout<<(i-1)*5;

    fin.close();
	fout.close();

	return 0;

}