#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb push_back
const ll mod = 1e9 + 7;
const ll N = 2e5 + 37;
template<typename T, size_t N>
std::ostream& operator<<(std::ostream& os, const std::array<T, N>& a);
template<typename T>
std::ostream& operator<<(std::ostream& os, const std::vector<T>& v);
template<typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, const std::pair<T1, T2>& p);
template<typename T>
std::ostream& operator<<(std::ostream& os, const std::set<T>& s);
template<typename T, typename cmp>
std::ostream& operator<<(std::ostream& os, const std::set<T, cmp>& s);
const ll inf = (ll)2e18 + 37;
ll get_period(ll a, ll b) {
ll ans = a / gcd(a, b + 1);
if(inf / ans < b) {
return -1;
}
return ans * b;
}
void solve_inf_case(ll n) {
ll ans = 0;
for(ll i = 0; i < n; ++i) {
ll l, r;
cin >> l >> r;
ans += r - l + 1;
}
cout << ans << endl;
}
void solve() {
ll n, A, B;
cin >> n >> A >> B;
ll period = get_period(A, B);
if(period == -1) {
solve_inf_case(n);
return;
}
set<pair<ll, ll> > s; // {r, l}
auto insert_p = [&](pair<ll, ll> p) -> void
{
assert(p.first >= p.second);
// cout << "Hey : " << p.second << ' ' << p.first << endl;
while(!s.empty() and p.second <= s.rbegin()->first) {
auto it = s.end();
--it;
p = {max(p.first, it->first), min(p.second, it->second)};
s.erase(it);
}
s.insert(p);
};
vector<pair<ll, ll> > a;
for(ll i = 0; i < n; ++i) {
pair<ll, ll> p; // {r, l}
cin >> p.second >> p.first;
bool twice = false;
if(p.first - p.second >= period - (p.second % period)) {
twice = true;
}
p.second %= period;
p.first %= period;
// cout << "Hi : " << p.second << ' ' << p.first << endl;
if(twice) {
a.push_back({period - 1, p.second});
a.push_back({p.first, 0});
}
else {
a.push_back(p);
}
}
sort(a.begin(), a.end());
for(const auto& p : a)
insert_p(p);
// cout << period << endl;
ll ans = 0;
for(auto p : s){
// cout << p.second << " " << p.first << endl;
ans += p.first - p.second + 1;
}
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// signed t; cin >> t; while(t--)
solve();
}
template<typename T, size_t N>
std::ostream& operator<<(std::ostream& os, const std::array<T, N>& a) {
os << "[";
for(size_t i = 0; i + 1 < N; ++i) {
os << a[i] << ", ";
}
if(N > 0)
os << a[N - 1];
os << "]";
return os;
}
template<typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, const std::pair<T1, T2>& p) {
os << "(" << p.first << ", " << p.second << ") ";
return os;
}
template<typename T>
std::ostream& operator<<(std::ostream& os, const std::vector<T>& v) {
os << '[';
for(auto x : v)
os << x << ", ";
os << "] ";
return os;
}
template<typename T>
std::ostream& operator<<(std::ostream& os, const std::set<T>& s) {
os << "{";
for(auto x : s)
os << x << ", ";
os << "} ";
return os;
}
template<typename T, typename cmp>
std::ostream& operator<<(std::ostream& os, const std::set<T, cmp>& s) {
os << "{";
for(auto x : s)
os << x << ", ";
os << "} ";
return os;
}
