#include <bits/stdc++.h>
#define F first
#define S second
#define lol ios::sync_with_stdio(false);cin.tie(NULL);
typedef int ll;
typedef long double ld;
using namespace std;
const ll M = 998244353;
int main() {
lol
ll n, a, b;
cin >> n >> a >> b;
vector<pair<ll,ll>> lr(n);
for(ll i=0; i<n; i++) cin >> lr[i].F >> lr[i].S;
ll m = a*b/gcd(a, b-1);
vector<pair<ll,ll>> in;
for(ll i=0; i<n; i++) {
if(lr[i].S - lr[i].F >= m - 1) {cout << m; return 0;}
ll d = ((lr[i].S)/m) * m;
if(d > lr[i].F) {
in.push_back({lr[i].F % m, m-1});
in.push_back({0, lr[i].S % m});
} else in.push_back({lr[i].F % m, lr[i].S % m});
}
sort(in.begin(), in.end());
in.push_back({m, m});
ll curmx = -1, cur = 0, ans = 0;
for(auto & x : in) {
if(x.F > curmx) {
ans += (curmx - cur + 1);
curmx = x.S, cur = x.F;
} else curmx = max(x.S, curmx);
}
cout << ans;
return 0;
}
