module main {
    // State variables
    var coin : int;
    var dispensed_drinks : int;

    // Initialize the state variables
    init {
        coin = 0;
        dispensed_drinks = 0;
    }

    // Define possible transitions
    next {
        // Model the insertion of a coin
        if (*) {
            coin' = coin + 1;
            dispensed_drinks' = dispensed_drinks;
        }
        // Model the dispensing of a drink
        else if (coin > dispensed_drinks) {
            coin' = coin;
            dispensed_drinks' = dispensed_drinks + 1;
        }
        else {
            coin' = coin;
            dispensed_drinks' = dispensed_drinks;
        }
    }

    // Safety property: Number of dispensed drinks should not exceed the number of coins
    invariant safety_property : dispensed_drinks <= coin;

    // Control block for verification
    control {
        v = unroll(10); // Adjust the depth of unrolling as needed
        check;
        print_results;
    }
}
