#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n,a,b;
cin>>n>>a>>b;
vector<pair<int,int>>v(n);
for(auto&[c,d]:v){
cin>>c>>d;
}
int g = __gcd(a,b+1);
g = a/g; // number of cycles required to get back the same x
__int128 tt= g;
tt*=b;
int mx = -1,ans=0;
vector<pair<int,int>>v1;
if(tt<=(__int128)1e18){
for (auto[c,d]:v){
if(d-c>tt){
ans=tt;
break;
}
int c1 = c%((int)tt);
int d1 = d%((int)tt);
if(c1>d1){
v1.push_back({c1,tt-1});
v1.push_back({0LL,d1});
}else{
v1.push_back({c1,d1});
}
}
}else{
for(auto[c,d]:v){
v1.push_back({c,d});
}
}
if(ans){
cout<<ans<<endl;
return 0;
}
sort(v1.begin(), v1.end());
for (auto[c,d]:v1){
if (c>mx){
ans+=d-c+1;
mx=d;
}else if(d>mx){
ans+=d-mx;
mx=d;
}
}
cout<<ans<<endl;
return 0;
}
