int r = 8 , b = 7;

void setup() {
  // put your setup code here, to run once:
  pinMode(r, OUTPUT);
  pinMode(b, INPUT_PULLUP);
}

void loop() {
  // put your main code here, to run repeatedly:
  
  int val = digitalRead(b);
  if(val == 0){
    digitalWrite(r,1);
  }
  else{
    digitalWrite(r,0);
  }
}