"use strict";
const input = require("fs").readFileSync("/dev/stdin", "utf8").trim();
const line = input.split('\n')[0].split(' ');
const H = +line[0];
const W = +line[1];
const p = Math.floor(H / 2);
const q = H - p;
const s = Math.floor((W + 1) / 2);
const t = Math.floor(W / 2);
const sum = p * s + q * t;
console.log(sum);