#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
#include <vector>
#include <set>
typedef long long llong;
const int MAXN = 1e6 + 10;
const llong INF = 1e18;
int n;
llong a, b;
llong l[MAXN];
llong r[MAXN];
std::vector <std::pair <llong, llong>> v;
void solve()
{
llong aPrim = a / std::__gcd(a, b + 1);
if (aPrim > INF / b)
{
llong sum = 0;
for (int i = 1 ; i <= n ; ++i)
{
sum += r[i] - l[i] + 1;
}
std::cout << sum << '\n';
return;
}
llong s = aPrim * b;
for (int i = 1 ; i <= n ; ++i)
{
if (r[i] - l[i] + 1 >= s)
{
std::cout << s << '\n';
return;
}
if (l[i] % s <= r[i] % s)
{
v.push_back({l[i] % s, r[i] % s});
} else
{
v.push_back({l[i] % s, s - 1});
v.push_back({0, r[i] % s});
}
}
llong sum = 0;
llong last = -1;
std::sort(v.begin(), v.end(), [&](auto x, auto y)
{
return x.second < y.second;
});
for (const auto &[l, r] : v)
{
sum += std::max(0LL, r - std::max(last, l - 1));
last = std::max(last, r);
}
std::cout << sum << '\n';
}
void input()
{
std::cin >> n >> a >> b;
for (int i = 1 ; i <= n ; ++i)
{
std::cin >> l[i] >> r[i];
}
}
void fastIOI()
{
std::ios_base :: sync_with_stdio(0);
std::cout.tie(nullptr);
std::cin.tie(nullptr);
}
int main()
{
fastIOI();
input();
solve();
return 0;
}
