//UNSTOPPABLE
#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp>
#define ll long long
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define int long long
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
#define pii pair<int,int>
#define tpii pair <pair <int,int> , int>
#define bruh cout << "NO\n"
using namespace std;
using namespace __gnu_pbds;
const int N = 3e5 + 5;
int mod = 1e9 + 7;
const int INF = 1e18;
int n,A,B;
void Goldik(){
cin >> n >> A >> B;
set <pii> st;
for(int i = 1 ; i <= n ; i++){
int l,r;
cin >> l >> r;
for(int j = l ; j <= r ; j++){
int x = ((j + (j / B)) % A) , y = (j % B);
st.insert({x , y});
}
}
cout << st.size();
}
//rewai mnogo zadach vozmozhno odna iz nih gde to popadetsya
//returning winter prime?
//chem prowe tem luchshe
signed main(/*AZ AZDAN UZDIKSIZ*/){
//freopen("txt.in","r",stdin);
//freopen("txt.out","w",stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
srand(time(0));
int TT = 1;
// cin >> TT;
for(int i = 1 ; i <= TT ; i++){
//cout << "Case " << i << ": ";
Goldik();
}
}
