void setup() {
Serial.begin(9600);
pinMode(2, OUTPUT);
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(1, INPUT);
}

void loop() {
float a = analogRead(A1);
float b = (a/1024)*100;
Serial.println(b);
if (b>= 1 && b<=20){digitalWrite(2, HIGH);}
if (b>=21 && b<=40){digitalWrite(2, HIGH);}
if (b>=21 && b<=40){digitalWrite(3, HIGH);}
if (b>=41 && b<=100){digitalWrite(2, HIGH);}
if (b>=41 && b<=100){digitalWrite(3, HIGH);}
if (b>=41 && b<=100){digitalWrite(4, HIGH);}

if (b>=1){
digitalWrite(2, LOW);
digitalWrite(3, LOW);
digitalWrite(4, LOW);


}
}