#include <iostream>
#include <fstream>

using namespace std;
int nr=0,q,n,x,i;
long long p;
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    if (p==1) {nr=1;g<<nr;}
    else
    while (p!=0)
    {
        nr=nr+5;
        if (nr%25==0) p=p-2;
        else p=p-1;
        if (p==0) {g<<nr;break;}
    }
    return 0;
}