#include<bits/stdc++.h>
#define overload(a,b,c,d,...) d
#define rep1(a) for(ll _=0;_<(ll)a;++_)
#define rep2(i,a) for(ll i=0;i<(ll)a;++i)
#define rep3(i,a,b) for(ll i=a;i<(ll)b;++i)
#define rep(...) overload(__VA_ARGS__,rep3,rep2,rep1)(__VA_ARGS__)
#define rrep1(i,a) for(ll i=(ll)a-1;i>=0;--i)
#define rrep2(i,a,b) for(ll i=(ll)b-1;i>=(ll)a;--i)
#define rrep(...) overload(__VA_ARGS__,rrep2,rrep1)(__VA_ARGS__)
#define all(a) a.begin(),a.end()
#define lb(v,x) lower_bound(all(v),x);
#define ub(v,x) upper_bound(all(v),x);
using namespace std;
using ll=long long;
using ull=unsigned long long;
using ld=long double;
template<typename T,typename U>
inline bool chmin(T&a,const U&b){return (a>b?a=b,true:false);}
template<typename T,typename U>
inline bool chmax(T&a,const U&b){return (a<b?a=b,true:false);}
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;cin>>n;
ll a,b;cin>>a>>b;
ll g=gcd(a,b+1);
if((ld)(1e18)/(ld)b<a/g){
ll ans=0;
rep(i,n){
ll l,r;cin>>l>>r;
ans+=r-l+1;
}
cout<<ans<<endl;return 0;
}
vector<pair<ll,ll>>v;
ll md=a/g*b;
rep(i,n){
ll l,r;cin>>l>>r;
if(r-l+1>=md){
cout<<md<<endl;return 0;
}
l%=md,r%=md;
if(l>r){
v.emplace_back(l,1);
v.emplace_back(md,-1);
v.emplace_back(0,1);
v.emplace_back(r+1,-1);
}
else{
v.emplace_back(l,1);
v.emplace_back(r+1,-1);
}
}
sort(all(v));
ll ans=0,cnt=1;
rep(i,1,v.size()){
if(cnt>0){
ans+=v[i].first-v[i-1].first;
}
cnt+=v[i].second;
}
cout<<ans<<endl;
}
