#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> II;
const int N = 1e6 + 5, logN = 20;
const int MOD = 1e9 + 7;
const ll INF = 1e18;
int n;
ll A, B, cyc, sum = 0;
vector<II> vt;
II seg[N];
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n >> A >> B;
for(int i = 1; i <= n; i ++) cin >> seg[i].first >> seg[i].second, sum += seg[i].second - seg[i].first + 1;
ll k = A / __gcd(A, B + 1);
if(k > INF / B + 1){
cout << sum << endl;
return 0;
}
cyc = k * B;
for(int i = 1; i <= n; i ++){
if(seg[i].second - seg[i].first + 1 >= cyc){
cout << cyc << endl;
return 0;
}
if(seg[i].first % cyc <= seg[i].second % cyc) vt.push_back(II(seg[i].first % cyc, seg[i].second % cyc));
else vt.push_back(II(0, seg[i].second % cyc)), vt.push_back(II(seg[i].first % cyc, cyc - 1));
}
sort(vt.begin(), vt.end());
ll Max = 0, ans = 0;
for(auto x : vt){
Max = max(Max, x.first);
ans += max(0ll, x.second - Max + 1);
Max = max(Max, x.second + 1);
}
cout << ans << endl;
return 0;
}
