function Main(input) {
  input = input.replace(/\n/g, ' ');
  input = input.split(" ");
  var A = Number(input[0]);
  var B = input[1].split(".");
  var C = Number(B[0]);
  var D = Number(B[1]);
  var ans = A*C + A*D/100;
  console.log(Math.floor(ans));
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));