//#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops")
//#pragma GCC target("avx,avx2")
//#pragma GCC target("avx2")
//#pragma GCC optimize("O3")
//# include <x86intrin.h>
# include <bits/stdc++.h>
# include <ext/pb_ds/assoc_container.hpp>
# include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
template<typename T> using ordered_set = tree <T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define _USE_MATH_DEFINES_
#define ll long long
#define ld long double
#define Accepted 0
#define pb push_back
#define mp make_pair
#define sz(x) (int)(x.size())
#define every(x) x.begin(),x.end()
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define For(i,x,y) for (ll i = x; i <= y; i ++)
#define FOr(i,x,y) for (ll i = x; i >= y; i --)
#define SpeedForce ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
// ROAD to... Red
void setIn(string s) { freopen(s.c_str(),"r",stdin); }
void setOut(string s) { freopen(s.c_str(),"w",stdout); }
void setIO(string s = "") {
// cin.exceptions(cin.failbit);
// throws exception when do smth illegal
// ex. try to read letter into int
if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
}
const double eps = 0.000001;
const ld pi = acos(-1);
const int maxn = 1e7 + 9;
const int mod = 1e9 + 7;
const ll MOD = 1e18 + 9;
const ll INF = 1e18 + 123;
const int inf = 2e9 + 11;
const int mxn = 1e6 + 9;
const int N = 6e5 + 123;
const int M = 22;
const int pri = 997;
const int Magic = 2101;
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};
mt19937 gen(chrono::steady_clock::now().time_since_epoch().count());
int rnd (int l, int r) {
return uniform_int_distribution<int> (l, r)(gen);
}
int n;
ll a, b;
vector < pair <ll, ll > > p;
int main () {
SpeedForce;
cin >> n >> a >> b;
p.resize(n);
for (auto &e : p) cin >> e.first >> e.second;
a = a / __gcd(a,b+1);
if (INF / a < b) {
ll ans = 0;
for (auto e : p) ans += e.second - e.first + 1;
cout << ans << '\n';
exit(0);
}
a *= b;
vector < pair<ll, ll> > e;
for (auto it : p) {
if((ll)(it.first / a) + 1 < (ll)it.second / a) {
cout << a << '\n';
exit(0);
}
if (it.second/a == it.first/a) e.pb({it.first%a, it.second%a});
else {
e.pb({it.first % a, a-1});
e.pb({0, it.second % a});
}
}
sort(every(e));
ll ans = 0;
for (int i = 0; i < sz(e); ++i) {
ll l, r;
tie(l,r) = e[i];
int j = i;
while(j + 1 < sz(e) && e[j+1].first <= r) {
++j;
r = max(r, e[j].second);
}
ans += r - l + 1;
i = j;
}
cout << ans << '\n';
return Accepted;
}
// B...a
