float v= 0;
float c=0;
float s =0;
void setup() 
{ 
  pinMode(1, OUTPUT);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
}

void loop() 
{
  const float BETA = 3950; 
  int analogValue = analogRead(A0);
  float c = 1 / (log(1 / (1023. / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;
  if(c<20)
  {
    digitalWrite(1, HIGH);
    delay(1000);
    digitalWrite(1, LOW);
  }
  else if(c>=20&&c<26)
  {
    digitalWrite(2, HIGH);
    delay(1000);
    digitalWrite(2, LOW);
  }
  else
  {
    digitalWrite(3, HIGH);
    delay(1000);
    digitalWrite(3, LOW);
  }
}