Master

#include <Wire.h>

int x = 0;

void setup() {
  // put your setup code here, to run once:
Wire.begin();

}

void loop() {
  // put your main code here, to run repeatedly:
Wire.beginTransmission(4);
Wire.write(x);
Wire.endTransmission();
x++;
if (x > 5) x = 0;
delay(1000);
Wire.beginTransmission(3);
Wire.write(x);
Wire.endTransmission();
x++;
if (x > 12) x = 0;
delay(400);

}