This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define sz size()
#define pii pair <ll, ll>
const int N = 1e7 + 5;
#define ll long long
#define pb push_back
vector <pii> v;
ll n, a, b, l[N], r[N];
int main () {
//	freopen ("input.txt", "r", stdin);
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin >> n >> a >> b;
	__int128 m = a / __gcd (a, b + 1) * b;
	for (int i = 1; i <= n; ++i) {
		cin >> l[i] >> r[i];
	}
	if (r[n] < m) {
		ll jog = 0;
		for (int i = 1; i <= n; ++i) {
			jog += r[i] - l[i] + 1;
		}
		cout << jog;
		return 0;
	}
	for (int i = 1; i <= n; ++i) {
		if (r[i] - l[i] + 1 >= m) {
			return cout << (ll)m, 0;
		}
		if (l[i] % m > r[i] % m) {
			v.pb ({l[i] % m, m - 1});
			v.pb ({0, r[i] % m});
		}
		else {
			v.pb ({l[i] % m, r[i] % m});
		}
	}
	sort (v.begin(), v.end());
//	for (auto i : v) {
//		cout << i.ff << " " << i.ss << "\n";
//	}
//	return 0;
	ll l1 = v[0].ff, r1 = v[0].ss, jogap = 0;
	for (int i = 1; i < (int)v.sz; ++i) {
		if (v[i].ff <= r1) r1 = max (r1, v[i].ss);
		
		else {
			jogap += r1 - l1 + 1;
			l1 = v[i].ff; 
			r1 = v[i].ss;
		}
	}
	jogap += r1 - l1 + 1;
	cout << jogap;
}
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