int sw = 2;
int led = 4;
int sw_ch = 0;
void setup() {
 pinMode(sw, INPUT_PULLUP);
 pinMode(led,4);
Serial.begin(9600);
}

void loop() {
int sw1 = digitalRead(sw);
if(sw1 == 0){
  
   if(sw_ch == 0){
   
          digitalWrite(led,1);
          
          sw_ch = 1;
   
          Serial.println("led on");
  }


      else{
            
            digitalWrite(led,0);
            sw_ch = 0;
            Serial.println("led off");
   
}
delay(1000);
}
}