#include<bits/stdc++.h>
#define pb push_back
#define pf push_front
//#define mp make_pair
#define F first
#define S second
#define ff first
#define ss second
#define str string
#define ll long long
#define ull unsigned ll
#define ld long double
#define pll pair<ll,ll>
#define plll pair<pll,ll>
#define pllll pair<pll,pll>
#define pld pair<ld,ld>
#define vi vector<int>
#define vl vector<ll>
#define vll vector<pll>
#define vlll vector<plll>
#define vllll vector<pllll>
#define vb vector<bool>
#define sz(x) (x).size()
#define fr front()
//#define tp top()
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define bk back();
#define rep(i,a,b) for(int i=a;i<b;++i)
//#pragma GCC target( "sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#pragma GCC optimize("Ofast,unroll-loops,fast-math,O3")
using namespace std;
const ld pi=acos(-1.0);
const ll e5=1e5;
const ll e6=1e6;
const ll e9=1e9;
const ll inf=1e18;
const ll mod=1e9+7;
const ll mod2=998244353;
const ll MOD=106710087877475399;
const ll N=1e6+10;
ll bpm(ll x,ll y,ll m){if(y==0)return 1%m;if(y==1)return x%m;ll p=bpm(x,y/2,m);
if(y%2==0)return p*p%m;else return p*p%m*x%m;}
ll bp(ll x,ll y){if(y==0)return 1;if(y==1)return x;ll p=bp(x,y/2);
if(y%2==0)return p*p;else return p*p*x;}
void solve(){
ll n,a,b,k,ans=0;
cin>>n>>a>>b;
k=a/gcd(a,b+1)*b;
vll v;
for(ll i=1;i<=n;i++){
ll l,r; cin>>l>>r;
if(l+k<=r){
cout<<k;
return;
}
l%=k, r%=k;
if(l<=r) v.pb({l,r});
else v.pb({l,k-1}), v.pb({0,r});
}
sort(all(v));
ll p=0;
for(auto [l,r]:v){
if(p>r) continue;
if(p<l) ans+=r-l+1, p=r+1;
else ans+=r-p+1, p=r+1;
}
cout<<ans;
return;
}
int main(/*Aldk*/){
ios_base::sync_with_stdio(false); cin.tie(NULL);
//freopen("sequence.in", "r", stdin);
//freopen("sequence.out ", "w", stdout);
//cout<<setprecision(9)<<fixed;
ll test=1;
//cin>>test;
for(ll i=1;i<=test;i++){
solve();
cout<<'\n';
}
return 0;
}
