import * as fs from "fs"

const main = (args: string[]): void => {
    const [N, M] = args[0].split(" ").map(x => Number(x))
    const LR = args.slice(1, -1).map(x => x.split(" ").map(v => Number(v)))

    LR.sort((x, y) => x[1] > y[1] ? 1 : -1)

    let ans = N
    let lst = -1

    for (let i = 0; i < M; i++) {
        let [l, r] = LR[i]
        if (l <= lst && lst <= r) continue
        ans--
        lst = r
    }
    console.log(ans)
}

main(fs.readFileSync('/dev/stdin', 'utf8').split("\n"));