code:
#include <bits/stdc++.h>
using namespace std;
#define lowbit(x) x&-x;
typedef long long ll;
const int N = 5e5 + 10;
int oldl, oldr, newl[N], newr[N], s[N * 2];
int n;
int tree[2 * N];
struct node{
    int l, r;
}a[N];

bool cmp(node a, node b){
    return a.r < b.r;
}

void add(int x, int d){
    while(x < 2 * N){
        tree[x] += d;
        x += lowbit(x);
    }
}

ll sum(int x){
    ll ans = 0;
    while(x > 0){
        ans += tree[x];
        x -= lowbit(x);
    }
    return ans;
}

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

    cin >> n;
    for(int i = 1;i <= n;i++){
        cin >> oldl >> oldr;
        newl[i] = oldl;
        newr[i] = oldr;
        s[i] = oldl;
        s[i + n] = oldr;
    }

    sort(s + 1, s + 1 + 2 * n);
    int cnt = n;
    for(int i = 1;i <= cnt;i++){
        newl[i] = lower_bound(s + 1, s + 1 + 2 * n, newl[i]) - s;
        newr[i] = lower_bound(s + 1, s + 1 + 2 * n, newr[i]) - s;
        a[i] = {newl[i], newr[i]};
    }

    sort(a + 1, a + 1 + cnt, cmp);
    ll ans = 0;
    for(int i = 1;i <= n;i++){
        // cout << a[i].l << " " << a[i].r << endl;
        auto l = a[i].l, r = a[i].r;
        ans += sum(r) - sum(l - 1);
        add(r, 1);
    }
    cout << ans;

    return 0;
}