#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
#define ll long long
#define pb push_back
#define sz(x) (int)(x).size()
#define mp make_pair
#define f first
#define s second
#define all(x) x.begin(), x.end()
#define D(x) cerr << #x << " is " << (x) << "\n";
#define ld long double
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>; ///find_by_order(),order_of_key()
template<class T1, class T2> ostream& operator<<(ostream& os, const pair<T1,T2>& a) { os << '{' << a.f << ", " << a.s << '}'; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<T>& a){os << '{';for(int i=0;i<sz(a);i++){if(i>0&&i<sz(a))os << ", ";os << a[i];}os<<'}';return os;}
template<class T> ostream& operator<<(ostream& os, const set<T>& a) {os << '{';int i=0;for(auto p:a){if(i>0&&i<sz(a))os << ", ";os << p;i++;}os << '}';return os;}
template<class T> ostream& operator<<(ostream& os, const multiset<T>& a) {os << '{';int i=0;for(auto p:a){if(i>0&&i<sz(a))os << ", ";os << p;i++;}os << '}';return os;}
template<class T1,class T2> ostream& operator<<(ostream& os, const map<T1,T2>& a) {os << '{';int i=0;for(auto p:a){if(i>0&&i<sz(a))os << ", ";os << p;i++;}os << '}';return os;}
int n;
ll a,b;
ll nzd(ll aa,ll bb)
{
if(bb==0)
return aa;
return nzd(bb,aa%bb);
}
int main()
{
scanf("%i %lld %lld",&n,&a,&b);
ll z=a/nzd(a,b+1);
ll first=LLONG_MAX;
if(LLONG_MAX/z>b)
first=z*b;
vector<pair<ll,int> > events;
for(int i=0;i<n;i++)
{
ll l,r;
scanf("%lld %lld",&l,&r);
if(r-l+1>=first)
{
printf("%lld\n",first);
return 0;
}
l%=first;
r%=first;
events.pb({l,1});
events.pb({r+1,-1});
if(l>r)
events.pb({first,-1}),events.pb({0,1});
}
int cnt=0;
ll last=0,ans=0;
sort(all(events));
for(auto p:events)
{
if(cnt)
ans+=p.f-last;
cnt+=p.s;
last=p.f;
}
printf("%lld\n",ans);
}
