#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
vector<ll> original;
int main() {
ll n, a, b;
cin >> n >> a >> b;
vector<pair<ll, ll>> v(n);
for (int i = 0; i < n; i++) cin >> v[i].first >> v[i].second;
ll gc = __gcd(a, b + 1);
bool smallEnough = (__int128_t(a) / gc * __int128_t(b) <= LONG_LONG_MAX);
ll cy = smallEnough ? a / gc * b : 0;
if (!smallEnough) {
for (int i = 0; i < n; i++) {
original.push_back(v[i].first);
original.push_back(v[i].second);
original.push_back(v[i].second + 1);
}
} else {
for (int i = 0; i < n; i++) {
original.push_back(v[i].first % cy);
original.push_back(v[i].second % cy);
original.push_back((v[i].second + 1) % cy);
}
original.push_back(0);
original.push_back(cy - 1);
original.push_back(cy);
}
sort(original.begin(), original.end());
original.resize(unique(original.begin(), original.end()) - original.begin());
map<ll, ll> mp;
for (int i = 0; i < (int)original.size(); i++) mp[original[i]] = i;
vector<int> pre(original.size() + 1);
for (int i = 0; i < n; i++) {
auto& p = v[i];
ll l = p.first, r = p.second;
if (smallEnough && r - l + 1 >= cy) {
cerr << "FULL" << endl;
cout << cy << endl;
return 0;
}
auto add = [&](ll L, ll R) {
pre[mp[L]]++;
pre[mp[R + 1]]--;
};
if (smallEnough) {
l %= cy;
r %= cy;
if (l > r) {
add(l, cy - 1);
add(0, r);
} else {
add(l, r);
}
} else {
add(l, r);
}
}
// for (int i = 1; i < pre.size(); i++) pre[i] += pre[i - 1];
int cur = 0;
ll ans = 0;
for (int i = 0; i < (int)pre.size() - 1; i++) {
cur += pre[i];
if (cur > 0) ans += original[i + 1] - original[i];
}
cout << ans << endl;
}
