#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <queue>
#include <bitset>
#define pb push_back
#define int long long
#define str string
using namespace std;
const int M = 1e9 + 7;
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n, a, b;
cin >> n >> a >> b;
vector<pair<int, int>> pr(n);
for (int i = 0; i < n; i++) cin >> pr[i].first >> pr[i].second;
int g = __gcd(a, b+1);
a /= g;
if (a * b >= 1e18+8800) {
int ans = 0;
for (auto p : pr) {
ans += p.second - p.first+1;
}
cout << ans;
return 0;
}
set<int> ses;
for (auto p : pr) {
int l = p.first, r = p.second;
if (l == r) {
ses.insert(l%(a*b));
} else {
l %= (a * b);
r %= (a * b);
if (r <= l) r += a * b;
for (int x = l; x <= r; x++) {
ses.insert(x % (a * b));
}
}
}
cout << ses.size();
}
