function MainC(input){
    const arr = input.trim().split(' ');
    const num1 = BigInt(arr[0]);
    const num2 = BigInt(Math.floor(arr[1]*100));
    console.log(String(num1*num2/BigInt(100)).replace('n',''))
}
MainC(require("fs").readFileSync("/dev/stdin", "utf8"));
