Algorithm turnOn(n)
//Pre-Condition: Lights 1...n are all off.
//Post-Condition: Lights1...n are all on.
if (n = 1) then Turn ON light 1
else { //n >=2
    if (n > 2) then turnOff(n-2)
    if (n > 2) then turnOff(n-2)
}
end //turnOn