#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e18+7;
const ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ii,ll>
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
int main(void){
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n,A,B;
cin>>n>>A>>B;
ll c = B;
ll g = __gcd(B+1,A);
A /= g;
ll maxi = 1e18 + 105;
if(maxi / c < A){
c = maxi;
}
else{
c *= A;
}
vector<ii>ex;
f(i,0,n){
ll l,r;
cin>>l>>r;
if(r - l + 1 >= c){
ex.pb(ii(0,c - 1));
}
else{
l %= c;
r %= c;
if(l <= r){
ex.pb(ii(l,r));
}
else{
ex.pb(ii(l,c-1));
ex.pb(ii(0,r));
}
}
}
sort(all(ex));
ll l = ex[0].F,r = ex[0].S;
ll ans = 0;
for(auto x:ex){
if(x.F <= r){
r = max(r,x.S);
}
else{
ans += r - l + 1;
l = x.F,r = x.S;
}
}
ans += r - l + 1;
cout<<ans<<"\n";
}
