#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define _size(x) (int)x.size()
#define BIT(i, x) ((x >> i) & 1)
#define MASK(n) ((1 << n) - 1)
#define REP(i, n) for (int i = 0, _n = (n); i < _n; i++)
#define FOR(i, a, b) for (int i = a, _b = (b); i <= _b; i++)
#define FORD(i, a, b) for (int i = a, _b = (b); i >= _b; i--)
#define FORB1(i, mask) for (int i = mask; i > 0; i ^= i & - i)
#define FORB0(i, n, mask) for (int i = ((1 << n) - 1) ^ mask; i > 0; i ^= i & - i)
#define FORALL(i, a) for (auto i: a)
#define fastio ios_base::sync_with_stdio(0); cin.tie(0);
const long long inf = 1e18;
int main() {
fastio;
int n;
long long a, b;
cin >> n >> a >> b;
long long k = a / __gcd(b + 1, a);
vector<pair<long long, int>> g;
long long p = 0;
if (inf / k < b) p = inf + 5;
else p = k * b;
REP(i, n) {
long long l, r;
cin >> l >> r;
if (r - l + 1 >= p) {
cout << p << '\n';
return 0;
}
long long lo = l % p, hi = r % p;
if (lo <= hi) g.push_back({lo, + 1}), g.push_back({hi, - 1});
else {
g.push_back({lo, + 1}), g.push_back({p - 1, - 1});
g.push_back({0, + 1}), g.push_back({hi, - 1});
}
}
sort(g.begin(), g.end(), [&] (const pair<long long, int> a, pair<long long, int> b) { return (a.fi != b.fi) ? (a.fi < b.fi) : (a.se > b.se); });
int i = 0, sum = 0;
long long ans = 0, cur;
while (i < _size(g)) {
int cur_sum = sum;
int j = i;
while (j < _size(g) && g[j].fi == g[i].fi && g[j].se == + 1) sum++, j++;
if (!cur_sum && sum) ans++;
else if (sum) ans += g[i].fi - cur;
while (j < _size(g) && g[j].fi == g[i].fi) sum--, j++;
cur = g[i].fi;
i = j;
}
cout << ans << '\n';
return 0;
}
