module main {
    // Define types and variables
    type state_t = enum { NONCRITICAL, TRY, WAIT, CRITICAL, EXIT };
    var s : [0:1];
    var y0 : boolean;
    var y1 : boolean;
    var pc0 : state_t;
    var pc1 : state_t;

    // Initial conditions
    init {
        s = 1;
        y0 = false;
        y1 = false;
        pc0 = NONCRITICAL;
        pc1 = NONCRITICAL;
    }

    // Process P0
    next(pc0) {
        case
            pc0 == NONCRITICAL : TRY;
            pc0 == TRY : { y0' = true; s' = 0; WAIT; }
            pc0 == WAIT : (y1 == 0 || s != 0) ? CRITICAL : WAIT;
            pc0 == CRITICAL : { y0' = false; EXIT; }
            pc0 == EXIT : NONCRITICAL;
            true : pc0;
        esac
    }

    // Process P1
    next(pc1) {
        case
            pc1 == NONCRITICAL : TRY;
            pc1 == TRY : { y1' = true; s' = 1; WAIT; }
            pc1 == WAIT : (y0 == 0 || s != 1) ? CRITICAL : WAIT;
            pc1 == CRITICAL : { y1' = false; EXIT; }
            pc1 == EXIT : NONCRITICAL;
            true : pc1;
        esac
    }

    // Property: Mutual Exclusion
    invariant mutual_exclusion : !(pc0 == CRITICAL && pc1 == CRITICAL);

    // Property: Starvation Freedom
    // Assuming fairness, each process should eventually reach CRITICAL if it keeps trying.
    invariant starvation_freedom_0 : pc0 != WAIT || (y1 == 0 || s != 0);
    invariant starvation_freedom_1 : pc1 != WAIT || (y0 == 0 || s != 1);
}
