/*
* Author: Nonoze
* Created: Tuesday 31/12/2024
*/
#include <bits/stdc++.h>
using namespace std;
#ifndef IN_LOCAL
#define dbg(...)
#endif
// #define cout cerr << "OUT: "
#define endl '\n'
#define endlfl '\n' << flush
#define quit(x) return (void)(cout << x << endl)
template<typename T> void read(T& x) { cin >> x;}
template<typename T1, typename T2> void read(pair<T1, T2>& p) { read(p.first), read(p.second);}
template<typename T> void read(vector<T>& v) { for (auto& x : v) read(x); }
template<typename T1, typename T2> void read(T1& x, T2& y) { read(x), read(y); }
template<typename T1, typename T2, typename T3> void read(T1& x, T2& y, T3& z) { read(x), read(y), read(z); }
template<typename T1, typename T2, typename T3, typename T4> void read(T1& x, T2& y, T3& z, T4& zz) { read(x), read(y), read(z), read(zz); }
template<typename T> void print(vector<T>& v) { for (auto& x : v) cout << x << ' '; cout << endl; }
#define sz(x) (int)(x.size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define make_unique(v) sort(all(v)), v.erase(unique(all(v)), (v).end())
#define pb push_back
#define mp(a, b) make_pair(a, b)
#define fi first
#define se second
#define cmin(a, b) a = min(a, b)
#define cmax(a, b) a = max(a, b)
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
#define QYES quit("YES")
#define QNO quit("NO")
#define int long long
#define double long double
const int inf = numeric_limits<int>::max() / 4;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD = 1e9+7, LOG=20;
void solve();
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
int tt=1;
// cin >> tt;
while(tt--) solve();
return 0;
}
__int128_t GCD(__int128_t a, __int128_t b) {
while (b) {
a%=b;
swap(a, b);
}
return a;
}
int n, A, B;
vector<pair<int, int>> a;
void solve() {
read(n, A, B);
a.clear(), a.resize(n); read(a);
__int128_t modulus=((__int128_t)A*B)/GCD((__int128_t)A* (__int128_t)B, B+1);
if (modulus>1e18) {
int ans=0;
for (int i=0; i<n; i++) {
ans+=a[i].se-a[i].fi+1;
}
cout << ans << endl;
return;
}
if (n==1) {
int ans=a[0].se-a[0].fi+1;
if (ans > modulus) ans=modulus;
cout << ans << endl;
return;
}
// a.clear(), a.resize(n); read(a);
for (A=1; A<=10; A++) {
for (B=1; B<=10; B++) {
bool ok=1;
map<pair<int, int>, bool> mp;
vector<pair<int, int>> is;
for (int i=0; i<1000; i++) {
int x=(i+i/B)%A, y=i%B;
if (mp.count({x, y})) {
if (ok) {
cout << A << " " << B << ' ' << i << ' ' << A*B/gcd(A*B, B+1) << endl;
if (i!=A*B/gcd(A*B, B+1)) cout << "NOOO" << endl;
}
if (is[i%sz(is)]!=mp(x, y)) {
cout << -1 << endl;
return;
}
ok=0;
continue;
}
if (!ok) {
cout << -1 << endl;
return;
}
mp[{x, y}]=1;
is.pb({x, y});
// dbg(x, y);
}
}
}
read(A, B);
map<pair<int, int>, bool> mp;
vector<pair<int, int>> is;
for (int i=0; i<1000; i++) {
int x=(i+i/B)%A, y=i%B;
if (mp.count({x, y})) {
cout << i << endl;
break;
}
mp[{x, y}]=1;
dbg(x, y);
}
}
