int ledpin=13;
int buttonpin=4;
boolean ledState=false;
void setup() {
pinMode(ledpin,OUTPUT);
pinMode(buttonpin,INPUT_PULLUP);
}

void loop() {
while(digitalRead(buttonpin)==HIGH){}
//int buttonState=digitalRead(buttonpin);
if(ledState==true){
digitalWrite(ledpin, HIGH);
ledState=!ledState;}
else{
digitalWrite(ledpin, LOW);
ledState=!ledState;
}
delay(500);
}