#include <bits/stdc++.h>
#define dbg() cerr <<
#define name(x) (#x) << ": " << (x) << ' ' <<
// 0(B+1) 1 2 3 ... B-2 B-1
// 1(B+1) B+2 B+3 B+4 ... 2B-1 2B
// 2(B+1) 2B+3 ....
// ---
// X(B+1)
// vreau ca X(B+1) = 0 (mod A) => X(B+1) multiplu de A => X(B + 1) = lcm(A, B + 1)
// X(B + 1) = A * (B + 1) / GCD(A, B + 1) => X = A / GCD(A, B + 1)
using namespace std;
const long long INF = numeric_limits<long long>::max();
long long GCD(long long a, long long b) {
if (!b) return a;
return GCD(b, a % b);
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
auto Print = [&](long long ans) {
cout << ans << endl;
exit(0);
};
long long n, a, b; cin >> n >> a >> b;
// for (int t = 0; t < 20; ++t) {
// dbg() (t + t / b) % a << ' ' << t % b << endl;
// }
vector<pair<long long, long long>> segm(n);
long long total = 0;
for (auto &p : segm) {
cin >> p.first >> p.second;
total += p.second - p.first + 1;
}
long long x = a / GCD(a, b + 1);
if (x >= INF / b) { // x e ft mare => in prima perioada
Print(total);
}
long long t = x * b; // perioada
// dbg() "perioada este " << name(t) endl;
vector<pair<long long, long long>> v; v.reserve(2 * n);
for (auto &p : segm) {
if (p.second - p.first + 1 >= t) {
Print(t);
}
p.first %= t; p.second %= t;
if (p.first <= p.second) {
v.emplace_back(p);
} else {
v.emplace_back(p.first, t - 1);
v.emplace_back(0LL, p.second);
}
}
sort(v.begin(), v.end());
long long rgt = -1, ans = 0LL;
for (auto &p : v) {
// dbg() name(p.first) name(p.second) endl;
if (p.second > rgt) {
ans += p.second - max(p.first, rgt + 1) + 1;
rgt = p.second;
}
}
Print(ans);
}
