// Problem: A - Strange Device
// Contest: Virtual Judge - 2024-02-27 APIO Simulation
// URL: https://vjudge.net/contest/612540#problem/A
// Memory Limit: 512 MB
// Time Limit: 5000 ms
//
// Powered by CP Editor (https://cpeditor.org)
#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define print(A,t) cerr << #A << ": "; copy(all(A),ostream_iterator<t>(cerr," " )); cerr << endl
#define prArr(A,n,t) cerr << #A << ": "; copy(A,A + n,ostream_iterator<t>(cerr," " )); cerr << endl
#define what_is(x) cerr << #x << " is " << x << endl
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef vector<int> vi;
int n; ll A, B;
const int MAXN = 1000010;
ll L[MAXN], R[MAXN];
void subtask1() {
set<pair<ll, ll>> ans;
for (int i = 1; i <= n; i++) {
for (ll j = L[i]; j <= R[i]; j++) {
ll x = (j + j / B) % A;
ll y = j % B;
ans.insert({x, y});
}
}
cout << sz(ans) << endl;
}
void subtask4() {
bool halved = false;
if (A % 2 == 0) {
A /= 2;
halved = true;
}
bool full = false;
vector<pair<ll, int>> events;
for (int i = 1; i <= n; i++) {
ll l = L[i] % A, r = R[i] % A;
if (R[i] - L[i] + 1 >= A) {
full = true;
break;
}
if (l <= r) {
events.push_back({l, -1});
events.push_back({r + 1, 1});
} else {
events.push_back({0, -1});
events.push_back({r + 1, 1});
events.push_back({l, -1});
events.push_back({A, 1});
}
}
if (full) {
cout << A << endl;
if (halved) A *= 2;
return;
}
ll ans = 0;
int open = 0;
sort(all(events));
ll cur_time = 0;
for (auto ev : events) {
// cout << ev.first << " " << ev.second << endl;
ll passed = ev.first - cur_time;
if (open > 0) ans += passed;
open -= ev.second;
cur_time = ev.first;
}
cout << ans << endl;
if (halved) A *= 2;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
cin >> n >> A >> B;
ll S = 0, SL = 0;
for (int i = 1; i <= n; i++) {
cin >> L[i] >> R[i];
S += (R[i] - L[i] + 1);
SL = max(SL, R[i] - L[i] + 1);
}
if (S <= 1000000) subtask1();
else if (B == 1) subtask4();
return 0;
}
