function main(input){
  input = input.split('\n');

  const [N, X, T] = input[0].split(' ').map(Number);
  let count = Math.trunc(N/X);
  if(N%X != 0) count += 1;

  console.log(count*T);

}

main(require('fs').readFileSync('/dev/stdin', 'utf8').trim());
