const int buttonPin = 4;  
const int ledPin = 2;
int i=0;   
int ledState = HIGH;        
int buttonState;            
int lastButtonState = LOW;  
unsigned long lastDebounceTime = 0;  
unsigned long debounceDelay = 50;   
void setup() {
pinMode(buttonPin, INPUT);
pinMode(ledPin, OUTPUT);
digitalWrite(ledPin, ledState);
Serial.begin(9600);}
void loop() {
int reading = digitalRead(buttonPin);
if (reading != lastButtonState) {
lastDebounceTime = millis();}
if ((millis() - lastDebounceTime) > debounceDelay) {
if (reading != buttonState) {
buttonState = reading;
if (buttonState == HIGH) {
ledState = !ledState;
digitalWrite(ledPin, ledState);
Serial.println(++i);
}}}
digitalWrite(ledPin, ledState);
lastButtonState = reading;}