#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll,ll>
#define F first
#define S second
const int N=1e6+10;
ll n,a,b,k,ans,li,ri,l[N],r[N];
vector<pii>v;
bool overflow(ll x,ll y){
if(log10(x)+log10(y)>=log10(4e18))return 1;
return 0;
}
bool cmp(pii a,pii b){
if(a.F!=b.F)return a.F<b.F;
return a.S>b.S;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cin>>n>>a>>b;
for(int i=0;i<n;i++)cin>>l[i]>>r[i];
if(overflow(a,(b+1)/(__gcd(a,b+1))))k=2e18;
else k=a*(b+1)/__gcd(a,b+1),k/=(b+1),k*=b;
//cout<<"k: "<<k<<'\n';
if(k>=1e18){
for(int i=0;i<n;i++)ans+=(r[i]-l[i]+1);
cout<<ans;
return 0;
}
for(int i=0;i<n;i++)if(r[i]-l[i]+1>=k){
cout<<k;
return 0;
}
for(int i=0;i<n;i++){
l[i]%=k;
r[i]%=k;
if(r[i]<l[i])v.push_back({l[i],k-1}),v.push_back({0,r[i]});
else v.push_back({l[i],r[i]});
}
li=-1,ri=-2;
sort(v.begin(),v.end(),cmp);
for(int i=0;i<v.size();i++){
if(v[i].F>ri)ans+=(ri-li+1),li=v[i].F,ri=v[i].S;
else if(v[i].S>ri)ri=v[i].S;
}
ans+=(ri-li+1);
cout<<ans;
return 0;
}
