和Daidly的题解的代码基本一样，就是过不了样例#2
尝试多种自救（调试，询问）都无果，求$\text{dalao}$支援一下

#include <bits/stdc++.h>
using namespace std;
int n, p, I[500005], J[500005], ans;
bool book[10][300005];
stack <int> s[10];
int main() {
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
    cin >> n >> p;
    for (int i = 1; i <= n; i++) cin >> I[i] >> J[i];
    for (int i = 1; i <= n; i++)
    for (int i = 1; i <= n; i++) {
        while (!s[I[i]].empty() && J[i] < s[I[i]].top()) {
            s[I[i]].pop();
            ans++;
        }
        if (!book[I[i]][J[i]]) {
            s[I[i]].push(J[i]);
            ans++;
        }
        book[I[i]][J[i]] = true;
    }
    cout << ans;
    return 0;
}