#include <iostream>
#include <iomanip>
#include <random>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <cmath>
#include <numeric>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <sstream>
#include <bitset>
#include <cassert>
#include <fstream>
#include <queue>
#define len(X) ((int)(X).size())
#ifdef __LOCAL
#define DBG(X) cout << #X << "=" << (X) << '\n';
#define SAY(X) cout << (X) << '\n';
#else
#define DBG(X)
#define SAY(X)
#endif
using namespace std;
using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for(auto el: v) cout << el << " "; return os; }
template<typename T> inline T fetch() { T ret; cin >> ret; return ret; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for(auto& elem: ret) cin >> elem; return ret; }
ll GCD(ll x, ll y) {
return (x == 0 ? y : GCD(y % x, x));
}
ll calc_period(ll A, ll B) {
ll k = (A / GCD(A, B + 1));
return k * B;
}
void solve() {
int n = fetch<int>();
ll A = fetch<ll>();
ll B = fetch<ll>();
set<ll> setik;
ll p = calc_period(A, B);
DBG(p);
for(int i = 0; i < n; ++i) {
ll L = fetch<ll>();
ll R = fetch<ll>();
for(ll x = L; x <= R; ++x) {
setik.insert(x % p);
}
}
cout << len(setik) << '\n';
}
int main() {
fast_io();
solve();
return 0;
}
