void setup() {
  pinMode(3, INPUT_PULLUP);
  pinMode(4,OUTPUT);
  digitalWrite(4, LOW);
  Serial.begin(9600);
  Serial.println("Aperte o botão!");
}

void loop() {
  bool estadoled;
  estadoled = digitalRead(4);
 
  while(digitalRead(3)==0){
    if(estadoled == 0){
      digitalWrite(4, HIGH);
    }else{
      digitalWrite(4, LOW);
    }
 }
}