#include<fstream>

using namespace std;

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

long long int P,p,nr,ind;

int main(){

    fin >> P;

    while(p<P){
        nr+=5;
        ind=nr;
        while (ind%5==0){
            ind=ind/5;
            p++;
        }
    }

    fout << nr;

    fin.close();
    gout.close();

}