#include <cmath>
#include <cassert>
#include <iostream>
#include <set>
#include <climits>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <type_traits>
#include <string>
#include <queue>
#include <map>
using namespace std;
class Intervals {
public:
set<pair<int64_t,int64_t>> intervals;
void print () {
for (auto& p: intervals) {
cout << p.first << " " << p.second << '\n';
}
cout << '\n';
}
pair<int64_t,int64_t> leftIntersect (pair<int64_t,int64_t> &p) {
auto it = intervals.upper_bound({p.first + 1, -1});
if (it == intervals.begin()) {
return {-1, -1};
}
it--;
pair<int64_t,int64_t> q = *it;
if (q.second < p.first) {
return {-1, -1};
}
return q;
}
pair<int64_t,int64_t> rightIntersect (pair<int64_t,int64_t> p) {
auto it = intervals.upper_bound({p.second + 1, -1});
if (it == intervals.begin()) {
return {-1, -1};
}
it--;
pair<int64_t,int64_t> q = *it;
if (q.first > p.second || q.first < p.first) {
return {-1, -1};
}
return q;
}
bool willChange (pair<int64_t,int64_t> p) {
pair<int64_t,int64_t> q = leftIntersect(p);
if (q.first < 0 && q.second < 0) {
return true;
}
if (q.first <= p.first && q.second >= p.second) {
return false;
}
return true;
}
pair<int64_t,int64_t> update_left (pair<int64_t,int64_t> p) {
pair<int64_t,int64_t> q = leftIntersect(p);
if (q.first == -1 && q.second == -1) {
return p;
}
if (q.second < p.first) {
return p;
}
intervals.erase(q);
return {q.first, p.second};
}
pair<int64_t,int64_t> update_right (pair<int64_t,int64_t> p) {
pair<int64_t,int64_t> q = rightIntersect(p);
if (q.first == -1 && q.second == -1) {
return p;
}
if (q.first > p.second) {
return p;
}
intervals.erase(q);
return {p.first, q.second};
}
void erase_in_between (pair<int64_t,int64_t> p) {
auto it = intervals.lower_bound({p.first, -1});
set<pair<int64_t,int64_t>> to_erase;
while (it != intervals.end()) {
if ((*it).second < p.second) {
to_erase.insert(*it);
} else {
break;
}
it++;
}
for (auto& q: to_erase) {
intervals.erase(q);
}
}
void add_interval (pair<int64_t,int64_t> p) {
if (!willChange(p)) {
return;
}
erase_in_between(p);
pair<int64_t,int64_t> new_p1 = update_right(update_left(p));
intervals.insert(new_p1);
}
};
int64_t gcd (int64_t a, int64_t b) {
if (!a || !b) return max(a,b);
return gcd(max(a,b) % min(a,b), min(a,b));
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int N;
int64_t A, B;
cin >> N >> A >> B;
A /= gcd(A, B + 1);
int64_t prod;
if (A < 1e18/B) {
prod = A * B;
} else {
prod = 1e18;
}
Intervals myInterval;
for (int i = 0; i < N; i++) {
int64_t x, y;
cin >> x >> y;
if (abs(y - x) >= prod) {
myInterval.add_interval({0, prod - 1});
continue;
}
x %= (prod), y %= (prod);
if (x <= y) {
myInterval.add_interval({x, y});
} else {
swap(x, y);
myInterval.add_interval({0, x});
myInterval.add_interval({y, prod - 1});
}
}
int64_t ans = 0;
for (auto& p: myInterval.intervals) {
ans += p.second - p.first + 1;
}
cout << ans << '\n';
}
