bwpoints.cpp

#include <bits/stdc++.h>
using namespace std;

int main() {
    if (fopen("in", "r")) {
        freopen("in", "r", stdin);
    }
    cin.tie(0)->sync_with_stdio(0);
    int n; cin >> n;
    vector<pair<int,int>> a(n * 2 + 1);
    for (int i = 1; i <= n; i++) {
        cin >> a[i].first;
        a[i].second = 1;
    }
    for (int i = n + 1; i <= n * 2; i++) {
        cin >> a[i].first;
        a[i].second = 0;
    }
    sort(a.begin() + 1, a.end());
    vector<int> last(2, -1);
    vector<int> dp(n * 2 + 1);
    for (int i = 1; i <= n * 2; i++) {
        int color = a[i].second;
        dp[i] = dp[i - 1];
        if (last[!color] != -1) {
            dp[i] = max(dp[i], dp[last[!color] - 1] + 1);
        }
        last[color] = i;
    }
    cout << dp[n * 2] << '\n';
}