#include <algorithm>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <queue>
#include <set>
#include <utility>
#include <vector>
using namespace std;

namespace solve
{
    const int maxn = 2.5e5 + 10;
    typedef pair<int, int> pii;

    int a[maxn], b[maxn];
    int n;

    int is[maxn], stk[maxn], top, lst[maxn];

    void main()
    {
        cin >> n;
        for (int i = 1; i <= n; i++)
            cin >> a[i] >> b[i];
        vector<vector<int>> all(n + 1);
        int tot = 0;
        auto work = [&](int *a)
        {
            top = 0;
            memset(is, 0, sizeof(is)), memset(lst, 0, sizeof(lst));
            vector<int> o(1000100);
            for (int i = 1; i <= n; i++)
                lst[i] = o[a[i]], o[a[i]] = i;
            for (int i = 1; i <= n; i++)
            {
                while (top > 0 && a[i] < a[stk[top]])
                    is[stk[top--]] = 0;
                is[stk[++top] = i] = 1;
                if (lst[i] && is[lst[i]])
                {
                    if (lst[i] < i - 1)
                        all[lst[i]].push_back(i - 1), tot++;
                }
            }
        };
        work(a), work(b);
        int ao = 0;
        for (int i = 1; i < n; i++)
            ao += a[i] != a[i + 1], ao += b[i] != b[i + 1];
        int match = 0;
        priority_queue<int> q;
        for (int i = 1; i < n; i++)
        {
            for (int x : all[i])
                q.push(-x);
            if (a[i] != a[i + 1] && b[i] != b[i + 1])
            {
                tot++;
                while (!q.empty() && -q.top() < i)
                    q.pop();
                if (!q.empty())
                {
                    q.pop();
                    match++;
                }
            }
        }
        cout << ao - tot + match << endl;
    }
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    solve::main();
}