function Main(input) {
	input = input.split("\n");
	tmp = input[0].split(" ");
	
	var n = parseInt(tmp[0], 10);
	var x = parseInt(tmp[1], 10);
	var t = parseInt(tmp[2], 10);
	
	//console.log("n:" + n);
	//console.log("x:" + x);
	//console.log("t:" + t);
	
	var a = Math.ceil(n / x);
	var result = a * t;
	
	console.log(result);
	}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));