//#pragma GCC optimize ("Ofast")
//#pragma GCC target("avx2")
//#pragma GCC optimize("unroll-loops")
//#include <x86intrin.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>
#define PI 3.141592653589793L
#define FAST ios::sync_with_stdio(false); cin.tie(NULL);
// Use for file I/O;
#define FIN string _fname = "input"; \
string _is = _fname + ".in", _os = _fname + ".out"; \
freopen(_is.c_str(), "r", stdin); \
freopen(_os.c_str(), "w", stdout);
#define FIN2 freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
#define RINIT mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define all(x) (x).begin(), (x).end()
#define allr(x) (x).rbegin(), (x).rend()
#define gsize(x) (int)((x).size())
using namespace std;
//using namespace __gnu_pbds;
//typedef gp_hash_table<int, int, hash<int>> ht;
const char nl = '\n';
typedef long long ll;
typedef long double ld;
// typedef unsigned int uint;
typedef unsigned long long ull;
const ll inf = 1e9 + 10;
const ll inf2 = 1e18 + 99LL;
const ld inf3 = 1e17;
const ll mod = 1e9+7, mod2 = 998244353;
const ld eps = 1e-9;
const bool local = false;
//RINIT;
const int logn = 21, maxn = 1000000, maxm = 100000, maxn2 = 3;
int main() {
FAST;
int n;
cin >> n;
ll a, b;
cin >> a >> b;
ll tn = a * b;
vector<ll> p(tn + 1);
vector<bool> good(tn);
while (n--) {
ll l, r;
cin >> l >> r;
if (r - l + 1 >= tn) {
p[0]++;
} else {
l %= tn;
r %= tn;
if (l <= r) {
p[l]++;
p[r + 1]--;
} else {
p[0]++;
p[r + 1]--;
p[l]++;
}
}
}
for (int i = 0; i < tn; i++) {
p[i + 1] += p[i];
good[i] = (p[i] > 0);
}
set<pair<ll, ll>> ts;
for (ll x = 0; x < tn; x++) {
if (good[x]) {
ts.emplace((x + x / b) % a, x % b);
}
}
cout << gsize(ts) << nl;
}
// © Benq
/* stuff you should look for
* int overflow, array bounds
* special cases (n=1?)
* do smth instead of nothing and stay organized
* WRITE STUFF DOWN
* DON'T GET STUCK ON ONE APPROACH
*/
