// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <unordered_map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
using namespace std;
#define int long long
#define endl "\n"
#define fi first
#define se second
const int M=1e9+7;
const int inf = 1e15;
const int LOG=17;
const int N=2e5+5;
int n , m , c , w , k , t=1 , q=1 , x , y , z , l , r;
int A,B;
void solve(){
cin >> n >> A >> B;
int g=__gcd(B+1,A);
A/=g;
if (log2(A)+log2(B)>=60){
A=B=1e9+1;
}
vector<pair<int,int>>a(n);
for (int i=0;i<n;i++){
cin >> a[i].fi >> a[i].se;
a[i].fi%=(A*B);
a[i].se%=(A*B);
if (a[i].se<a[i].fi){
a.push_back({0,a[i].se});
a[i].se=A*B-1;
}
}
sort(a.begin(),a.end());
n=a.size();
for (int i=1;i<n;i++){
a[i-1].se=min(a[i].fi-1,a[i-1].se);
}
c=n;
for (int i=0;i<n;i++){
c+=a[i].se-a[i].fi;
}
cout << c << endl;
}
signed main()
{
// #ifndef ONLINE_JUDGE
// freopen("input.txt","r" ,stdin);
// freopen("output.txt","w",stdout);
// #endif
ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE
cin.tie(0), cout.tie(0);//DO NOT USE IN INTERACTIVE
cout << fixed << setprecision(9);
srand(time(0));
// int t=1;
// cin >> t;
for (int _=1;_<=t;_++){
solve();
q++;
}
}
