题目链接：区间合并

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

const int N = 100010;

typedef pair<int, int> PII;
int n;
vector<PII> segs;

void merge(vector<PII> &segs)
{
    vector<PII> res;
    sort(segs.begin(), segs.end());
    int st = -2e9, ed = -2e9;
    for(auto item: segs)
    {
        if(ed < item.first){
            if(st != -2e9) res.push_back({st, ed});
            st = item.first, ed = item.second;
        }
        else ed = max(ed, item.second);
    }
    // 处理最后一个区间
    if(st != -2e9) res.push_back({st, ed});
    segs = res;
}

int main()
{
    cin >> n;
    while(n--)
    {
        int l, r;
        cin >> l >> r;
        segs.push_back({l, r});
    }
    merge(segs);
    cout << segs.size() << endl;
    return 0;
}