acwing803区间合并

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
typedef pair<int ,int> PII;
vector<PII>regs;
int N=100010;
void merge(vector<PII>&regs){
    vector<PII> ans;
    sort(regs.begin(),regs.end());
    int l=-2e9,r=-2e9;
    for(auto reg:regs){
        if(reg.first>r){
            if(r!=-2e9)ans.push_back({r,l});
            l=reg.first;
            r=reg.second;
        }else r=max(r,reg.second);
    }
    if(l!=-2e9)ans.push_back({l,r});
    regs=ans;
}
int main(){
    int n;
    cin>>n;
    while(n--){
        int x,c;
        cin>>x>>c;
        regs.push_back({x,c});
    }
    merge(regs);
    cout<<regs.size()<<endl;
    return 0;
}