#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, a, b;
cin >> n >> a >> b;
int sum = 0;
vector<int> l(n), r(n);
for (int i = 0; i < n; i++) {
cin >> l[i] >> r[i];
sum += r[i] - l[i] + 1;
}
int g = gcd(a, b + 1);
if (__int128(a) * b / g > r[n - 1]) {
cout << sum << '\n';
return 0;
}
int k = a / g * b;
for (int i = 0; i < n; i++) {
if (r[i] - l[i] + 1 > k) {
cout << k << '\n';
return 0;
}
}
for (int i = 0; i < n; i++) {
l[i] %= k;
r[i] %= k;
}
vector<int> x, y;
for (int i = 0; i < n; i++) {
if (l[i] <= r[i]) {
x.push_back(l[i]); y.push_back(r[i]);
} else {
x.push_back(l[i]); y.push_back(k - 1);
x.push_back(0); y.push_back(r[i]);
}
}
int sz = x.size();
vector<int> ord(sz);
iota(ord.begin(), ord.end(), 0);
ranges::sort(ord, [&](int i, int j) {
return x[i] < x[j];
});
int mx = -1, ans = 0;
for (auto i : ord) {
if (x[i] <= mx) {
ans += max(0LL, y[i] - mx);
mx = max(mx, y[i]);
} else {
ans += y[i] - x[i] + 1;
mx = y[i];
}
}
cout << ans << '\n';
return 0;
}
