const int ledpin=14;
const int buttonpin=12;
int buttonstate=0;
int present_temp=0;
int previous_temp=0;

void setup() 
{
  // put your setup code here, to run once:
  pinMode(ledpin,OUTPUT);
  pinMode(buttonpin,INPUT);
}

void loop() 
{
  // put your main code here, to run repeatedly:
  buttonstate=digitalRead(buttonpin);
  if (buttonstate==HIGH)
  {
    present_temp=buttonstate;
    if(previous_temp!=present_temp)
       { 
        digitalWrite(ledpin,HIGH);
        previous_temp=present_temp;
       }
    else
    {
      digitalWrite(ledpin,LOW);
      previous_temp=0;
    }
  }
}