#include "bits/stdc++.h"
using namespace std;
#define int long long
#define all(x) x.begin(),x.end()
#define ff first
#define ss second
#define pb push_back
template<class T, class U> inline bool chmin(T& a, const U& b) { if (a > b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmax(T& a, const U& b) { if (a < b) { a = b; return true; } return false; }
const int inf = 1e18;
const int mod = 1e9 + 7;
const int N = 2e5+5;
void solve(){
map<array<int,2>,int> mp;
int n, a, b;
cin >> n >> a >> b;
for(int i =0 ; i < n; i++){
int l, r;
cin >> l >> r;
for(int t = l; t <= r; t++){
mp[{(t+t/b)%a, t%b}] = 1;
}
}
cout << mp.size() << '\n';
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
int t = 1;
//cin >> t;
while(t--){
solve();
}
}
