#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;
#ifdef _WIN32
#define getchar_unlocked _getchar_nolock
#endif
#define int long long
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define ppb pop_back
#define eb emplace_back
#define g0(a) get<0>(a)
#define g1(a) get<1>(a)
#define g2(a) get<2>(a)
#define g3(a) get<3>(a)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
typedef double db;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
typedef tuple<int, int, int, int> iiii;
typedef tree<ii, null_type, less<ii>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
int N, A, B, P, f = -1, st, ans;
vector<ii> seg;
main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> N >> A >> B;
P = A / __gcd(A, B + 1) * B;
assert(P <= 1e18);
for (int i = 1, l, r; i <= N; i++) {
cin >> l >> r;
if (r - l + 1 >= 2 * P) return cout << P << '\n', 0;
if (l + P - (l % P) > r) seg.eb(l % P, r % P);
else seg.eb(l % P, P - 1), seg.eb(0, r % P);
}
sort(seg.begin(), seg.end());
for (auto i : seg) {
if (i.first > f) {
if (f != -1) ans += f - st + 1;
st = i.first;
}
f = max(f, i.second);
}
ans += f - st + 1;
cout << ans << '\n';
}
