#include <bits/stdc++.h>
using namespace std;
#define all(a) (a).begin(), (a).end()
#define add push_back
#define pll pair<long long, long long>
#define ll long long
#define fr first
#define sc second
const int N = 1e6 + 5;
ll n, a, b;
ll k, h;
pll rng[N];
vector<pll> v;
void add_range(ll x, ll y){
if(x <= y){
v.add({x, 0});
v.add({y, 1});
}
else {
v.add({x, 0});
v.add({h - 1, 1});
v.add({0, 0});
v.add({y, 1});
}
}
void solve(){
cin >> n >> a >> b;
ll cnt = 0;
for(int i = 0; i < n; i++){
cin >> rng[i].fr >> rng[i].sc;
cnt += rng[i].sc - rng[i].fr + 1;
}
k = a / __gcd(a, b + 1);
ll maxk = 2'000'000'000'000'000'000ll / b;
if(k >= maxk){
cout << cnt << "\n";
return;
}
h = k * b;
for(int i = 0; i < n; i++){
if((rng[i].sc - rng[i].fr + 1) / h > 0){
cout << h << "\n";
return;
}
add_range(rng[i].fr % h, rng[i].sc % h);
}
sort(all(v));
ll ans = 0, opnd = 0, last = -1;
for(auto& [tiv, id] : v){
if(opnd) ans += tiv - last;
else ans++;
last = tiv;
if(id) opnd--;
else opnd++;
}
cout << ans << "\n";
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
solve();
return 0;
}
