import java.io.PrintWriter
import java.lang.Exception
import java.util.*

fun PrintWriter.solve() {
    val n = nextInt()
    val m = nextInt()
    val segs = mutableListOf<Pair<Int, Int>>()
    for (i in 0 until m) {
        val l = nextInt()
        val r = nextInt()
        segs.add(l to r)
    }
    segs.sortBy { it.second }
    var count = 0
    var prev = -1
    for ((l, r) in segs) {
        if (prev in l..r) continue
        count++
        prev = r
    }
    println(n - count)
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve()
    writer.flush()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()
fun nextDouble() = next().toDouble()
// endregion