var doors=[]; for (var i=0;i<100;i++) doors[i]=false; for (var i=1;i<=100;i++) for (var i2=i-1;i2<100;i2+=i) doors[i2]=!doors[i2]; for (var i=1;i<=100;i++) console.log("Door %d is %s",i,doors[i-1]?"open":"closed")