#include <bits/stdc++.h>
#define all(x) x.begin(),x.end()
#define sz(x) ((int)x.size())
#define pll pair<ll, ll>
#define MP make_pair
#define PB push_back
using namespace std;
typedef long long ll;
vector<pll> vc;
int n;
ll A, B;
int main(){
#ifdef _LOCAL
freopen("in.txt","r",stdin);
#else
ios_base::sync_with_stdio(0); cin.tie(0);
#endif // _LOCAL
cin >> n >> A >> B;
for (int i = 0; i < n; i++){
ll l, r; cin >> l >> r;
for (ll t = l; t <= r; t++)
vc.PB(MP((t + t / B) % A, t % B));
}
sort(all(vc));
vc.resize(unique(all(vc)) - vc.begin());
cout << sz(vc);
return 0;
}
