Problem with code

What is wrong with my code. We are programming "traffic lights" with LED on Arduino put I get a message saying that the program can't find the file. This is my code:
int knapp = 0;

void setup ()
{

pinMode(10,OUTPUT);
pinMode(12,OUTPUT);
pinMode(1,OUTPUT);
pinMode(3,OUTPUT);
pinMode(6,OUTPUT);
pinMode(8,OUTPUT);
pinMode(7,INPUT);

}

void loop()
{
digitalWrite(12, HIGH);
digitalWrite(6, HIGH);
digitalWrite(1, LOW);
digitalWrite(3, LOW);
delay(3000);
digitalWrite(12, LOW);
digitalWrite(10, HIGH);
delay(3000);
digitalWrite(10, LOW);
digitalWrite(1, HIGH);
delay(3000);

knapp = digitalRead(7);

if (knapp == LOW)
{
digitalWrite(12, LOW);
digitalWrite(1, LOW);
digitalWrite(10, HIGH);
digitalWrite(3, LOW);
digitalWrite(6, HIGH);

delay(3000);
digitalWrite(1, HIGH);
digitalWrite(10, LOW);
digitalWrite(12, LOW);
delay(1000);
digitalWrite(3, HIGH), tone(8, 450, 3000);
digitalWrite(6, LOW);
delay(3000);
digitalWrite(6, HIGH);
digitalWrite(3, LOW);
digitalWrite(1, LOW);
digitalWrite(10, HIGH);
delay(3000);
digitalWrite(10, LOW);
digitalWrite(12, HIGH);

delay(3000);
} }

What is wrong with your code? - It is not posted between code tags. ( </> at the top left of the ‘Post’ window. )

You should have read this before posting anything:- How to use this forum
(Item #7.)

And post the full error message too, also between code tags.