function areaCalculation(input){
    let figure = input[0];

    if ( figure === "square" ){
        let a = Number(input[1]);
        console.log((a * a).toFixed(3));
    }

    else if ( figure === "rectangle"){
        let a = Number(input[1]);
        let b = Number(input[2]);
        console.log((a * b).toFixed(3));
    }

    else if ( figure === "circle"){
        let r = Number(input[1]);
        console.log((Math.PI * Math.pow(r , 2)).toFixed(3));
    }

    else ( figure === "triangle")
        let a = Number(input[1]);
        let b = Number(input[2]);
        console.log(((a * b) / 2).toFixed(3) );







}
//areaCalculation(["square", "5"]);
//areaCalculation(["rectangle", "7", "2.5"]);
areaCalculation(["circle", "6"]);
//areaCalculation(["triangle", "4.5", "20"]);