题解 | #剩下的树#

#include <iostream>
#include<vector>
using namespace std;

int main() {
    int L, M, boxmin, boxmax,n = 1;
    cin >> L >> M;
    std::vector<int>tree(L, 1);
    while (M > 0) {
        cin >> boxmin >> boxmax;
        for(int i = boxmin-1;i<boxmax;++i){
            tree[i]=0;
        }
        M--;
    }
    for(int j = 0;j<L;j++){
        if(tree[j]==1){
            n+=1;
        }
    }
    std::cout<<n<<std::endl;

}