#include <bits/stdc++.h>
using namespace std; 
typedef long long i64; 

int n; i64 a, b; 
vector<pair<i64, i64>> v; 

int main(void) {
    ios::sync_with_stdio(0); cin.tie(0); 
    cin >> n >> a >> b;
    i64 T = a / __gcd(a, b + 1); 
    if ((__int128)T * b >= 1e18) T = 1e18;
    else T *= b;
    for (int i = 1; i <= n; i++) {
        i64 l, r; cin >> l >> r; 
        if (r - l + 1 >= T) return cout << T << "\n", 0; 
        l %= T, r %= T; 
        if (l <= r) v.emplace_back(l, r); 
        else v.emplace_back(l, T - 1), v.emplace_back(0, r); 
    }
    sort(v.begin(), v.end()); 
    i64 l = v[0].first, r = v[0].second, ans = 0; 
    for (auto p : v)
        if (p.first <= r) r = max(r, p.second);
        else ans += r - l + 1, l = p.first, r = p.second; 
    ans += r - l + 1; 
    cout << ans << "\n"; 
    return 0;
}