#pragma GCC optimize("Ofast,unroll-loops")
// #pragma comment(linker, "/stack:200000000")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma,tune=native")
#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;
typedef long long ll;
typedef long double ld;
typedef pair <ll, ll> pll;
#ifdef SINA
#define dbg(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << std::endl; }
template <typename Arg1, typename... Args> void __f (const char* names, Arg1&& arg1, Args&&... args) {
const char* comma = strchr(names + 1, ',');cout.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...); }
#define dbg2(x, j, n) cout<< #x << " : "; output((j), (n), x, 1);
#else
#define dbg(...) 0
#define dbg2(x, j, n) 0
#endif
#define SZ(x) ((ll)((x).size()))
#define File(s, t) freopen(s ".txt", "r", stdin); freopen(t ".txt", "w", stdout);
#define input(j, n, a) for (int _i = (j); _i < (n)+(j); _i++) cin>> a[_i];
#define output(j, n, a, t) for (int _i = (j); _i < (n)+(j); _i++) cout<< a[_i] << (((t) && _i != (n)+(j)-1)? ' ' : '\n');
#define kill(x) return cout<< x << endl, 0
#define cl const ll
#define fr first
#define sc second
// #define lc (v << 1)
// #define rc (lc | 1)
#define mid ((l + r) >> 1)
#define All(x) (x).begin(), (x).end()
cl inf = sizeof(ll) == 4 ? (1000000010) : (1000000000000000001LL), mod = 1e9 + 7, MOD = 998244353;
template <class A, class B> ostream& operator << (ostream& out, const pair<A, B> &a) {
return out << '(' << a.first << ", " << a.second << ')'; }
template <class A> ostream& operator << (ostream& out, const vector<A> &a) {
if(a.empty())return out<<"[]";out<< '[' << a[0]; for (int i = 0; ++i < (int)(a.size());) out<< ", " << a[i];out<< ']'; }
template <class T, typename _t = less <T> > using Tree = tree <T, null_type, _t, rb_tree_tag, tree_order_statistics_node_update>;
ll n, A, B, md, ans, cnt, L, t;
map <ll, vector <ll>> mp;
inline void add (cl &l, cl &r) { mp[l].push_back(1), mp[r + 1].push_back(-1); }
int main ()
{
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>> n >> A >> B;
md = A / __gcd(A, B + 1);
if (inf / B < md) md = inf;
else md = md * B;
for (ll l, r; n--;) {
cin>> l >> r;
if (r - l + 1 >= md) t = md;
l %= md, r %= md;
if (l <= r) add(l, r);
else add(0, r), add(l, md - 1);
}
for (auto &x : mp) {
if (cnt) ans += x.fr - L;
L = x.fr;
for (auto &y : x.sc) cnt += y;
}
cout<< max(ans, t) << endl;
return 0;
}
/*
3 3 3
4 4
7 9
17 18
3 5 10
1 20
50 68
89 98
2 16 13
2 5
18 18
*/
