module main {
    // State representation
    var green1, red1, green2, red2 : boolean;

    init {
        // Initial states
        green1 = false; red1 = true; // Traffic light 1 starts red
        green2 = true; red2 = false; // Traffic light 2 starts green
    }

    // Transition system
    next {
        // Action A: Traffic light 1 goes green, Traffic light 2 goes red
        if (red1 && green2) {
            green1' = true; red1' = false;
            green2' = false; red2' = true;
        }
        // Action B: Traffic light 1 goes red, Traffic light 2 goes green
        else if (green1 && red2) {
            green1' = false; red1' = true;
            green2' = true; red2' = false;
        }
    }

    // Check for deadlock
    invariant no_deadlock: (green1 != green2) && (red1 != red2);

    control {
        check;
        print_results;
    }
}
