Сшка

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

void mcin() {}

template<typename T, typename ...Tail>
void mcin(T &&arg, Tail &&...args) {
    cin >> arg;
    mcin(args...);
}
#define in(type, ...) type __VA_ARGS__; mcin(__VA_ARGS__);

template<typename T1, typename T2>
istream &operator>>(istream &in, pair<T1, T2> &p) {
    return in >> p.first >> p.second;
}

template<typename T>
istream &operator>>(istream &in, vector<T> &v) {
    for (auto &item: v)
        in >> item;
    return in;
}

#define all(c) c.begin(), c.end()

int main() {

    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    in(int, n, x, y)
    vector<pair<int, int>> a(n);
    cin >> a;

    function<ll(int, int)> solve = [&](int l, int r) {
        if (r - l == 1) {
            int len = a[l].second - a[l].first;
            return len >= x && len <= y ? 1ll : 0ll;
        }

        int m = (l + r) / 2;
        ll res = solve(l, m) + solve(m, r);

        vector<int> rl(r - m), rr(r - m);
        rl[0] = a[m].first, rr[0] = a[m].second;
        for (int i = m + 1; i < r; i++) {
            rl[i - m] = max(rl[i - m - 1], a[i].first);
            rr[i - m] = min(rr[i - m - 1], a[i].second);
        }

        int ll = 0, lr = 1e9;
        auto len = [&](int ptr) {
            return max(0, min(lr, rr[ptr]) - max(ll, rl[ptr]));
        };
        int ptr1 = r - m - 1, ptr2 = r - m - 1;
        for (int i = m - 1; i >= l; i--) {
            ll = max(ll, a[i].first);
            lr = min(lr, a[i].second);
            while (ptr1 >= 0 && len(ptr1) <= y) ptr1--;
            while (ptr2 >= 0 && len(ptr2) < x) ptr2--;
            res += ptr2 - ptr1;
        }

        return res;
    };

    cout << solve(0, n) << '\n';

}