#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#define str string
#define append push_back
#define vector deque
#define vi vector<int>
#define int long long
#define yes cout<<"YES"<<endl;
#define no cout<<"NO"<<endl;
#define endl '\n'
#define all(ls) ls.begin(),ls.end()
#define sorted(ls) sort(ls.begin(),ls.end());
#define reversed(ls) reverse(ls.begin(),ls.end());
#define print(n) for(auto i:n)cout<<i<<' ';cout<<endl;
#define input(n,ls,m) deque<n>ls(m);for(int i=0;i<m;i++)cin>>ls[i];
#define len(s) s.size()
#define ff first
#define ss second
#define N (int const) 3e5+1
#define pii pair<int,int>
#define SQ(x) ((x)*(x))
#define float double
int mod=1e9+7;
int mod1=998244353;
int sum_(vector<int>ls){int s=0;for(auto i:ls){s+=i;}return s;}
int min(int a,int b){if (a>b){return b;}return a;}
int max(int a,int b){if (a<b){return b;}return a;}
//......................................tHe ReaL cOdE beGinS HerE....................................../
int solve2(vector<pii> ls,int a,int b){
map<pair<int,int>,bool>m;
for(auto i:ls){
for(int j=i.ff;j<=i.ss;j++){
m[{(j+j/b)%a,j%b}]=1;
}
}
return len(m);
}
void solve(){
int n,a,b;
cin>>n>>a>>b;
vector<pii>ls;
int cnt=0;
for(int i=0;i<n;i++){
int x,y;
cin>>x>>y;
cnt+=y-x+1;
ls.append({x,y});
}
if(cnt<=1e6){cout<<solve2(ls,a,b)<<endl;return;}
a/=gcd(a,b+1);
a*=b;
for(auto i:ls){
if(i.ss-i.ff+1>=a){
cout<<a<<endl;return;
}
}
vector<pii>q;
for(auto i:ls){
int f=i.ff%a,s=i.ss%a;
if(f<s or i.ff==i.ss) q.append({f,s});
else{
q.append({f,a-1});
q.append({0,s});
}
}
sorted(q);
map<int,int>hlpr;
for(auto i:q) hlpr[i.ff]=i.ss;
vector<pii>q2;
for(auto i:hlpr) q2.append(i);
hlpr.clear();
swap(q2,q);
for(int i=1;i<q.size();i++){
if(q[i-1].ss>=q[i].ff){
q[i].ss=max(q[i].ss,q[i-1].ss);
q[i].ff=q[i-1].ff;
hlpr[i-1]=1;
}
}
q2.clear();
int ans=0;
for(int i=0;i<q.size();i++){
if(hlpr[i]){continue;}
ans+=q[i].ss-q[i].ff+1;
}
cout<<ans<<endl;
}
signed main(){
int t=1;
// cin>>t;
while(t--)
solve();
}
