"use strict"
const create = () => {
    const input = require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n");
    const res = {
        "list": input, "index": 0, "max": input.length,
        "hasNext": function () { return this.index < this.max },
        "next": function () { if (!this.hasNext()) { throw "ArrayIndexOutOfBoundsException"; } else { return this.list[this.index++]; } }
    };
    return res;
}
const o = create();
const next = () => o.next()
const nextInt = () => parseInt(o.next())
const nextStrArray = () => o.next().split(" ")
const nextIntArray = () => o.next().split(" ").map(el => parseInt(el))
const nextCharArray = () => o.next().split("")
const hasNext = () => o.hasNext()
const myout = (...x) => console.log(...x)
const Main = () => {
    let [h, w] = next().split(" ").map(el => BigInt(el))
    let first, second
    let firstRow, secondRow

    if(w == 1n || h == 1n){
        console.log(1)
        return
    }

    if (w % 2n == 0n) {
        first = w / 2n
        second = w / 2n
    } else {
        first = w / 2n + 1n
        second = w / 2n
    }
    if (h % 2n == 0n) {
        firstRow = h / 2n
        secondRow = h / 2n
    } else {
        firstRow = h / 2n + 1n
        secondRow = h / 2n
    }
    console.log((first * firstRow + second * secondRow).toString())
}
Main()
