#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
using ll = long long;
using int128 = __int128_t;
using pll = pair<ll, ll>;
template <class T>
using vec = vector<T>;
template <class T>
using indexed_set =
tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define FOR(i, s, e) for (ll i = (ll)s; i < (ll)e; i++)
#define CFOR(i, s, e) for (ll i = (ll)s; i <= (ll)e; i++)
#define TRAV(e, a) for (const auto &e : a)
#define all(x) x.begin(), x.end()
#define dbg(x) cerr << "ln" << __LINE__ << ": " << #x << " = " << x << endl;
template <class T, class = decay_t<decltype(*begin(declval<T>()))>,
class = enable_if_t<!is_same<T, string>::value>>
ostream &operator<<(ostream &out, const T &obj) {
out << "[";
for (auto it = obj.begin(); it != obj.end(); it++) {
out << &", "[2 * (it == obj.begin())] << *it;
}
return out << "]";
}
template <class K, class V>
ostream &operator<<(ostream &out, const pair<K, V> &obj) {
return out << "(" << obj.first << ", " << obj.second << ")";
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n, a, b;
cin >> n >> a >> b;
ll sz = min((int128)a * b / gcd(a, b + 1), (int128)1e18 + 5);
set<pll> ss;
auto insert = [&](pll p) {
auto it = ss.lower_bound(p);
while (it != ss.end() && it->first <= p.second) {
p.second = max(p.second, it->second);
it = ss.erase(it);
}
if (it != ss.begin() && p.first <= prev(it)->second) {
p.first = min(p.first, prev(it)->first);
p.second = max(p.second, prev(it)->second);
ss.erase(prev(it));
}
ss.insert(p);
};
FOR(i, 0, n) {
ll l, r;
cin >> l >> r;
if (r - l + 1 >= sz) {
insert({0, sz - 1});
} else {
l %= sz;
r %= sz;
if (l <= r) {
insert({l, r});
} else {
insert({0, r});
insert({l, sz - 1});
}
}
}
ll ans = 0;
TRAV(e, ss) ans += e.second - e.first + 1;
cout << ans << "\n";
}
