#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define dbg(...) 47
#endif
#define int long long
constexpr int inf = 1e18;
int a, b;
array<int, 2> get(int t) {
int x = (t + t / b) % a;
int y = t % b;
return {x, y};
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n >> a >> b;
int sum = 0;
vector<int> l(n), r(n);
for (int i = 0; i < n; i++) {
cin >> l[i] >> r[i];
sum += r[i] - l[i] + 1;
}
int g = gcd(a, b + 1);
if (__int128(a) * b / g >= inf) {
cout << sum << '\n';
return 0;
}
int x = a / g * b;
for (int i = 0; i < n; i++) {
l[i] %= x;
r[i] %= x;
}
vector<int> p(x + 1);
for (int i = 0; i < n; i++) {
if (l[i] <= r[i]) {
p[l[i]] += 1;
p[r[i] + 1] -= 1;
} else {
p[l[i]] += 1;
p[x] -= 1;
p[0] += 1;
p[r[i] + 1] -= 1;
}
}
for (int i = 1; i <= x; i++) {
p[i] += p[i - 1];
}
int ans = 0;
for (int i = 0; i < x; i++) {
ans += p[i] > 0;
}
cout << ans << '\n';
return 0;
}
