int led_1 = 12;
int led_2 = 8;
int buz = 5;
void setup() {
pinMode(led_1, OUTPUT);
pinMode(led_2, OUTPUT);
}

void loop() {
digitalWrite(led_1, HIGH);
digitalWrite(led_2, LOW);
tone(buz,250);
delay(1000);
digitalWrite(led_1, LOW);
digitalWrite(led_2, HIGH);
tone(buz,350);
delay(1000);
}