#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;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define int long long
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define vi vector<int>
#define vii vector<vi>
#define ld long double
#define pii pair<int, int>
mt19937 mt(time(0));
namespace io
{
template <typename T, typename F>
istream &operator>>(istream &cin, pair<T, F> &pr)
{
cin >> pr.first >> pr.second;
return cin;
}
template <typename T, typename F>
ostream &operator<<(ostream &cout, pair<T, F> &pr)
{
cout << pr.first << ' ' << pr.second;
return cout;
}
template <typename T>
istream &operator>>(istream &cin, vector<T> &vec)
{
for (T &i : vec)
cin >> i;
return cin;
}
template <typename T>
ostream &operator<<(ostream &cout, vector<T> vec)
{
for (T i : vec)
cout << i << ' ';
return cout;
}
}
using namespace io;
void solve()
{
int n, a, b;
int inf = 2e18;
cin >> n >> a >> b;
vector<pii> v(n);
cin >> v;
int A = a / __gcd(a, b + 1);
int m;
if (inf / A < b)
{
sort(all(v));
int R = -1;
int ans = 0;
for (auto &[l, r] : v)
{
if (r < R)
continue;
ans += r - max(l, R + 1) + 1;
R = max(R, r);
}
cout << ans;
return;
}
else
{
m = A * b;
for (auto &[l, r] : v)
{
int x = l / m;
l -= x * m;
r -= x * m;
if (r - l + 1 >= m)
return cout << m, void();
}
vector<pii> nw;
for (auto &[l, r] : v)
{
if (r < m)
nw.push_back({l, r});
else
{
nw.push_back({l, m - 1});
nw.push_back({0, r - m});
}
}
v = nw;
sort(all(v));
int R = -1;
int ans = 0;
for (auto &[l, r] : v)
{
if (r < R)
continue;
ans += r - max(l, R + 1) + 1;
R = max(R, r);
}
cout << ans;
}
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
while (t--)
solve(), cout << '\n';
return 0;
}
