process.stdin.resume();
process.stdin.setEncoding('utf8');

var input_lines = []; 
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
reader.on('line', (line) => {
  input_lines.push(line);
});
reader.on('close', () => {
  var height = input_lines[0].split(' ')[0];
  var width = input_lines[0].split(' ')[1];
  var count = 0;

  var odd = Math.ceil(height / 2);
  var even = height - odd;
  var movable_even = Math.floor(width / 2);
  var movable_odd = width % 2 === 1 ? movable_even + 1 : movable_even
  
  count = (even * movable_even) + (odd * movable_odd);
  
  console.log(count);
  
});