function Main(input) {
	var str = input;
	var ans = 1;
	var str = str.split("\n");
	var a = BigInt(str[0].split(" ")[0]);
	var b = str[0].split(" ")[1];
	b = b.replace('.', '');
	b = BigInt(b);
	ans = a*b;
	ans = ans.toString();
	ans = ans.slice( 0, -2 );
	if(ans === ""){
		ans = "0";
	}
	console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
