function Main(input) {
  input = input.split(" ");
  
  const N = parseInt(input[0], 10);
  const X = parseInt(input[1], 10);
  const T = parseInt(input[2], 10);
  
  var laps = N % X ? Math.floor(N / X) + 1 : Math.floor(N / X);
  var time = laps * T;
  
  console.log("%d", time);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));