解法：若区间覆盖的最小值大于等于2，则有他没他没影响，反之则不能算。所以一开始差分数组预处理区间加，然后ST表查最小值即可。

package com.sky;

import java.util.Scanner;
import java.util.Arrays;

public class Test1 {
    static final int maxn = 200005;
    static int n, m;
    static int[][] st = new int[maxn][30];
    static int[] d = new int[maxn];
    static int[] a = new int[maxn], b = new int[maxn];

    public static int query(int l, int r) {
        int k = (int)(Math.log(r - l + 1) / Math.log(2));
        return Math.min(st[l][k], st[r - (1 << k) + 1][k]);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();

        for (int i = 1; i <= m; ++i) {
            a[i] = sc.nextInt();
            b[i] = sc.nextInt();
            d[a[i]]++;
            d[b[i] + 1]--;
        }

        for (int i = 1; i <= n; ++i) {
            d[i] += d[i - 1];
            st[i][0] = d[i];
        }

        for (int j = 1; (1 << j) <= n; j++) {
            for (int i = 1; i + (1 << j) - 1 <= n; i++) {
                st[i][j] = Math.min(st[i][j - 1], st[i + (1 << (j - 1))][j - 1]);
            }
        }

        int res = 0;
        for (int i = 1; i <= m; ++i) {
            if (query(a[i], b[i]) >= 2) res++;
        }

        System.out.println(res);
        sc.close();
    }
}