import std.stdio;
import std.conv;
import std.string;

void main()
{
    string s = readln().chomp;
    if (s[$ - 1] == '0' ||
        s[$ - 1] == '2' || 
        s[$ - 1] == '4' ||
        s[$ - 1] == '6' ||
        s[$ - 1] == '8' ) {
        writeln(s);
    } else {
        writeln(s.to!(int) * 2);
    }
}
