process.stdin.resume();
process.stdin.setEncoding('utf8');
var lines = [];
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
reader.on('line', (line) => {
  lines.push(line);
});
reader.on('close', () => {
  var w = lines[0].split(' ');
  var n = parseInt([0]);
  var x = parseInt([1]);
  var t = parseInt([2]);
  var c = Math.floor(n / x + 1) * t;
  console.log(c);
});