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

    const result = a * b / BigInt(100);

    console.log(String(result));    
}

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