function area(input) {
    let figureType = input.shift(2);
    let area = 0.0;
    switch (figureType) {
        case "square": {
            let a = input.shift(2);
            area = a * a;
            break;
        }
        case "rectangle": {
            let a = input.shift(2);
            let b = input.shift(2);
            area = a * b;
            break;
        }
        case "circle": {
            let a = input.shift(2);
            area = Math.PI * a * a;
            break;
        }
        case "triangle": {
            let a = input.shift(2);
            let b = input.shift(2);
            area = 2 * b +a;
            break;

        }
    }console.log(area.toFixed(3));
}
area(['circle',6]);