#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)
m = inf;
else
m = A * b;
set<int> st;
for (auto &[l, r] : v)
for (int i = l; i <= r; i++)
st.insert(i % m);
cout << st.size();
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
while (t--)
solve(), cout << '\n';
return 0;
}
