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 N = parseInt(lines[0].split(' ')[0]);
  var X = parseInt(lines[0].split(' ')[1]);
  var T = parseInt(lines[0].split(' ')[2]);
  
  var totalT = Math.ceil(N / X) * T;
  console.log(totalT);
});