#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair <int , int>
#define F first
#define S second
const int N = 1e6 + 5, inf = 1e18 + 10;
vector <pii> seg;
int32_t main() {
int n, A, B, ans = 0; cin >> n >> A >> B;
A = A / __gcd(A, B + 1);
int AB = A*B;
if (inf/(long double)A <= B) {
for (int i = 0,l,r; i < n; i++) cin >> l >> r, ans += r - l + 1;
cout << ans << "\n";
return 0;
}
for (int i = 0; i < n; i++) {
int l, r; cin >> l >> r;
int L = l + (l % AB ? AB - l % AB : 0);
if (L + AB <= r + 1) return cout << AB << "\n", 0;
if (l/AB == r/AB) seg.push_back({l % AB, r % AB});
else seg.push_back({l % AB, AB - 1}), seg.push_back({0, r % AB});
}
sort(seg.begin(), seg.end());
int cl = seg[0].F, cr = seg[0].S;
for (pii p : seg) {
int l = p.F, r = p.S;
if (l <= cr) cr = max(cr, r);
else ans += cr - cl + 1, cl = l, cr = r;
}
cout << ans + cr - cl + 1 << "\n";
return 0;
}
