var math = {
    1 : function() {
        var a = prompt("A: "), b = prompt("B: "), c = prompt("C: ")
        alert (
            a == "?" && "A = " + Math.sqrt(Math.pow(c, 2) - Math.pow(b, 2)) ||
            b == "?" && "B = " + Math.sqrt(Math.pow(c, 2) - Math.pow(a, 2)) ||
            c == "?" && "C = " + Math.sqrt(Math.pow(a, 2) + Math.pow(b, 2)) ||
            "error, invalid parameters"
        )
    },
    2 : function() {
        var r = prompt("R: "), t = prompt("T: "), d = prompt("D: ")
        alert (
            r == "?" && "R = " + d / t ||
            t == "?" && "T = " + d / r ||
            d == "?" && "D = " + r * t ||
            "error, invalid parameters"
        )
    }
}

while (true) {
    math[parseInt(prompt(
        "1) Pythagorean Theorem (a² + b² = c²)\n" +
        "2) Distance (rt = d)\n"
    ))]()
}