function solve(input) {

    let type = Number(input.shift());
    let result = 0;

    if (`type===square`) {
        let sideA = Number(input.shift());
        result = sideA * sideA;

        //poluchavam 49.000
    } else if (type === `rectangle`) {
        let sideA = Number(input.shift())
        let sideB = Number(input.shift())
        result = sideA * sideb
        //poluchavam 20.250
    } else if (type = `triangle`) {
        let sideA = Number(input.shift());
        let sideB = Number(input.shift());
        result = sideA * sideB / 2;
        ////poluchavam 36.000
    } else {
        let r = Number(input.shift);
        result = Math.pow(r, 2) * Math.PI;
    }
    console.log(result.toFixed(3))
}



solve([
    `

])