calc.c

int led1 = 13;
int led2 =12;
int button=7;
int value=0;
int ledon=0;// 0 = led off, 1 = led on

// the setup routine runs once when you press reset:
void setup() {
  // initialize the digital pin as an output.
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(button,INPUT);
}

// the loop routine runs over and over again forever:
void loop() {
  value = digitalRead(button);
  if (value == HIGH){
    ledon= ledon+1;
    if(ledon== 4){ 
      (ledon=0);
    }
    delay(100);
  }
  
  if ((ledon == 1)||(ledon==3)) {
    digitalWrite(led1, HIGH);
  } else {
    digitalWrite(led2, LOW);
  }
  if ((ledon==2)||(ledon==3)) {
    digitalWrite(led1, HIGH);
  } else {
    digitalWrite(led1, LOW);
  }
}