#pragma GCC optimize("Ofast,fast-math,unroll-loops")
#include <bits/stdc++.h>
#define int ll
//#define double long double
#define endl '\n'
#define all(C) (C).begin(), (C).end()
#define rall(C) (C).rbegin(), (C).rend()
#define mp make_pair
#define pb emplace_back
#define dbg(x) cerr << #x << " : " << x << endl
//#define PI 3.141592653589
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair <int, int>;
using pld = pair <ld, ld>;
/*
const ll MAX_MEM = 4e8;
char MEM[MAX_MEM];
ll MEM_POS = 0;
void* operator new(size_t x)
{
auto ret = MEM + MEM_POS;
MEM_POS += x;
assert(MEM_POS < MAX_MEM);
return ret;
}
void operator delete(void*)
{}
*/
template <class T>
istream& operator>> (istream &in, vector <T> &a)
{
for (auto &i : a)
in >> i;
return in;
}
template <class T>
ostream& operator<< (ostream &out, vector <T> a)
{
for (auto &i : a)
out << i << ' ';
return out;
}
template <class T, class U>
istream& operator>> (istream &in, pair <T, U> &p)
{
in >> p.first >> p.second;
return in;
}
template <class T, class U>
ostream& operator<< (ostream &out, pair <T, U> p)
{
out << p.first << " " << p.second << " ";
return out;
}
inline void Start()
{
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
//freopen("lol.in", "r", stdin);
//freopen("lol.out", "w", stdout);
}
const int OPEN = 0, CLOSE = 1;
struct event
{
int x, t;
event() {}
event(int x, int t) : x(x), t(t) {}
};
signed main()
{
Start();
int n, a, b;
cin >> n >> a >> b;
int k = a / gcd(a, b + 1);
int t = k * b;
vector <event> e;
for (int i = 0; i < n; ++i)
{
int l, r;
cin >> l >> r;
if (l / t == r / t)
{
e.pb(l % t, OPEN);
e.pb(r % t + 1, CLOSE);
continue;
}
if (l / t + 1 == r / t)
{
if (r - l + 1 < t)
{
e.pb(l % t, OPEN);
e.pb(t, CLOSE);
e.pb(0, OPEN);
e.pb(r % t + 1, CLOSE);
continue;
}
}
cout << t;
return 0;
}
sort(all(e), [] (event a, event b) {return a.x < b.x || (a.x == b.x && a.t < b.t);});
int lst = -1, bal = 0, ans = 0;
for (auto f : e)
{
if (f.t == OPEN)
{
++bal;
if (bal == 1)
lst = f.x;
}
else
{
--bal;
if (!bal)
{
ans += f.x - lst;
}
}
}
cout << ans;
return 0;
}
