#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
    long p,i,ok=0,d=0,c=0,nr,m;
    fin>>p;
    for(i=1;ok==0;++i)
    {
        if(i%2==0&&i%5==0){++c;++d;}
        else if(i%2==0)++d;
        else if(i%5==0)++c;
        m=c;
        if(d<c)m=c;
        if(m==p){nr=i;ok=1;}

    }
    fout<<nr;
    return 0;
}