#include <bits/stdc++.h>
using namespace std;
#define ll unsigned long long
const int nx=1e6+5;
ll n, a, b, l[nx], r[nx], sm, p, mx, res, tmp;
set<pair<ll, ll>> s;
void add_range(ll x, ll y)
{
x=x%p;
y=y%p;
if (y<x) y+=p;
s.insert({x, min(p-1, y)});
if (y>=p) s.insert({0, y-p});
}
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>a>>b;
for (int i=1; i<=n; i++) cin>>l[i]>>r[i], mx=max(mx, r[i]-l[i]+1), sm+=(r[i]-l[i]+1);
tmp=a/__gcd(a, b+1);
if ((double) tmp * (double) (b) >= LLONG_MAX) return sm, 0;
p=tmp*b;
if (mx>=p) return cout<<p, 0;
for (int i=1; i<=n; i++) add_range(l[i], r[i]);
//for (auto [x, y]:s) cout<<"val "<<x<<' '<<y<<'\n';
for (auto itr=s.begin(); itr!=s.end()&&next(itr)!=s.end();)
{
auto itr2=next(itr);
pair<ll, ll> nw;
if (itr2->first>itr->second+1) itr=itr2;
else nw={itr->first, max(itr->second, itr2->second)}, s.erase(itr), s.erase(itr2), s.insert(nw), itr=s.find(nw);
}
for (auto [x, y]:s) res+=y-x+1;
cout<<res;
}
