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