#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
int n,s1,s2,s,p,i;
ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
s=0;
s1=0;
s2=0;
i=0;
while(s!=p)
{
        i++;
    if(i%10==2 || i%10==5)
        s1++;
    if(i%10==0)
        s2++;
    if(s1%2==0)
        s=s1+s2;
}
    f.close();
    g<<i;
    g<<"\n";
    g.close();
    return 0;
}