using static System.Console;

interface Expr {
    int eval();
}

record Const(int i) : Expr {
    public int eval() => i;
}

record BinOp(Expr e, string op, Expr f) : Expr {
    public int eval() {
        int x = e.eval(), y = f.eval();
        return op switch {
            "+" => x + y,
            "-" => x - y,
            "*" => x * y,
            "/" => x / y,
            "%" => x % y,
            _ => throw new Exception("bad operation")
        };
    }
}

class Top {
    static void Main(string[] args) {
        if (args.Length < 1) {
            WriteLine("usage: p2 <file.p2>");
            return;
        }
        Parser p = new(File.ReadAllText(args[0]));
        WriteLine(p.parse_expr().eval());
    }
}