const Main = input => {
    input = input.trim();
    input = input.split(" ");
    const a = BigInt(parseInt(input[0], 10));
    const b = BigInt(parseInt(input[1] * 100, 10));//小数 * 100 -> 整数

    const tmp = String(a * b);

    const result = tmp.substring(0, tmp.length - 3) + "." + tmp.substring(tmp.length - 2, tmp.length);

    console.log(Math.floor(parseInt(result)));    
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));