#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3,unroll-loops")
using namespace std;
#define int long long
#define pii pair<int,int>
#define ff first
#define ss second
#define sp << " " <<
#define all(cont) cont.begin(),cont.end()
#define vi vector<int>
const int inf = 1e18,N = 3e5+1,MOD = 998244353,BL = 1000;
void solve() {
int n,A,B;
cin >> n >> A >> B;
vi l(n+1),r(n+1);
for (int i=1;i<=n;i++) cin >> l[i] >> r[i];
if (A/__gcd(A,B+1) > (inf)/B) {
int sm = 0;
for (int i=1;i<=n;i++) sm+=r[i]-l[i]+1;
cout << sm << '\n';
return;
}
int p = A/__gcd(A,B+1)*B;
for (int i=1;i<=n;i++) {
if (r[i]-l[i]+1 >= p) {
cout << p << '\n';
return;
}
}
vector<pii> segs;
for (int i=1;i<=n;i++) {
l[i]%=p;
r[i]%=p;
if (l[i] <= r[i]) {
segs.push_back({l[i],r[i]});
}
else {
segs.push_back({l[i],p-1});
segs.push_back({0,r[i]});
}
}
sort(all(segs));
int uni = 0;
int mx = -1;
for (auto it : segs) {
uni+=max(0ll,it.ss-max(mx+1,it.ff)+1);
mx = max(mx,it.ss);
}
cout << uni << '\n';
}
int32_t main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#ifdef Dodi
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
