// You can't change other people; you can only change yourself.
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
// Pragmas
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
// Namespaces
#define yume using
#define wo namespace
#define kanaeyo std
#define nazotte __gnu_pbds
yume wo kanaeyo;
yume wo nazotte;
// Data types
using i8 = __int128;
using ll = long long;
using si = short int;
using ld = long double;
// Pairs
using pi8 = pair<i8, i8>;
using pll = pair<ll, ll>;
using pii = pair<int, int>;
using psi = pair<si, si>;
using pld = pair<ld, ld>;
#define fi first
#define se second
// PBDS
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
// Quick macro functions
#define sqr(x) ((x)*(x))
#define pow2(x) (1ll << (x))
#define debug(x) cout << #x << " = " << (x) << '\n'
#define debugV(x, a) cout << #x << "[" << (a) << "] = " << (x[a]) << '\n'
// Check min and max
template<typename T> void chmin(T &a, T b) {a = min(a, b);}
template<typename T> void chmax(T &a, T b) {a = max(a, b);}
// Modular arithmetic
template<typename T> void maddto(T &a, T b, T mod) {a += b; a %= mod;}
template<typename T> void msubto(T &a, T b, T mod) {a -= b; while (a < 0) a += mod; a %= mod;}
template<typename T> void mmulto(T &a, T b, T mod) {a *= b; a %= mod;}
template<typename T> T madd(T a, T b, T mod) {a += b; a %= mod; return a;}
template<typename T> T msub(T a, T b, T mod) {a -= b; while (a < 0) a += mod; return a;}
template<typename T> T mmul(T a, T b, T mod) {a *= b; a %= mod; return a;}
// Constants
const ll ModA = 998244353;
const ll ModC = 1e9 + 7;
const ll INF = 1e18;
const ll iINF = 1e9;
const ld EPS = 1e-9;
const ld iEPS = 1e-6;
i8 gcd(i8 x, i8 y) {
if (!y) return x;
return gcd(y, x % y);
}
ll n, A, B;
vector<pi8> segments;
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
scanf("%lld %lld %lld", &n, &A, &B);
i8 _A = A, _B = B;
i8 _loop = ((i8)1 * _A * _B) / gcd(_A, _B+1);
ll loop;
if (_loop >= INF) {
loop = INF;
} else {
loop = _loop;
}
for (ll l, r, i = 1; i <= n; i++) {
scanf("%lld %lld", &l, &r);
if (r - l + 1 >= loop) {
printf("%lld\n", loop);
return 0;
} else {
ll lx = l % loop, rx = r % loop;
if (lx <= rx) {
segments.push_back({lx, 1});
segments.push_back({rx+1, -1});
} else {
segments.push_back({0, 1});
segments.push_back({rx+1, -1});
segments.push_back({lx, 1});
segments.push_back({loop, -1});
}
}
}
sort(segments.begin(), segments.end());
ll ans = 0, depth = 0, lastOpen = -1;
for (auto &[pos, d] : segments) {
if (depth == 0) {
lastOpen = pos;
}
depth += d;
if (depth == 0) {
ans += pos - lastOpen;
}
}
printf("%lld\n", ans);
}
