#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 1e6 + 66;
int n; ll A, B;
vector<pair<ll,ll>> v;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
cin >> n >> A >> B;
ll g = gcd(A, B + 1), I;
if (A / g > ll(2e18) / B) {
I = ll(2e18);
} else {
I = A * B / g;
}
for (int i = 1 ; i <= n ; ++ i) {
ll l, r;
cin >> l >> r;
if (r - l + 1 >= I) {
cout << I << "\n";
return 0;
}
ll L = l % I, R = r % I;
if (L <= R) {
v.emplace_back(L, +1);
v.emplace_back(R + 1, -1);
} else {
v.emplace_back(0, +1);
v.emplace_back(R + 1, -1);
v.emplace_back(L, +1);
v.emplace_back(I, -1);
}
}
sort(v.begin(), v.end());
ll k = 0, l = -1, Ans = 0;
for (auto [i, t] : v) {
if (t == +1) {
if (k++ == 0) l = i;
} else if (--k == 0) Ans += i - l, l = i;
}
cout << Ans;
}
