#include <LiquidCrystal.h>

const int a = 12 , b = 11 , c = 5 , d = 4 , e = 3 , f = 2 ;
LiquidCrystal lcd ( a , b , c , d , e , f );
bool choice = 0;
int sx = 8;
int pt = 0;
int rx = 9;
int st = 0;

void setup() 
{
 lcd.begin(16, 2);
 pinMode(sx, INPUT_PULLUP);
 pinMode(rx, INPUT_PULLUP);  
}
void loop() 
{
 if (choice) 
 {
  pt = millis() - st;
 }

 if (digitalRead(sx) == 0) 
 {
    if (choice) 
    {
      choice = 0;
    } 
      else 
      {
        choice = 1;
        st = millis() - pt;
      }
    delay(50);
 }

 if (digitalRead(rx) == 0) {
    pt = 0;
    choice = false;
    delay(50);
 }

 lcd.setCursor( 0 , 0 );
 lcd.print("Time in sec is :");
 lcd.setCursor(0 , 1 );
 lcd.print(pt / 1000 );
 lcd.print(".");
 lcd.print((pt / 100) % 10);
 delay(100);

}