/*
ID: varunra2
LANG: C++
TASK: device
*/
#include <bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif
#define int long long
#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (int)1e9
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second
const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef map<int, int> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions
int32_t main() {
// #ifndef ONLINE_JUDGE
// freopen("device.in", "r", stdin);
// freopen("device.out", "w", stdout);
// #endif
cin.sync_with_stdio(0);
cin.tie(0);
int n, a, b;
cin >> n >> a >> b;
int gc = __gcd(a, b + 1);
// t = b * x
// b*x + x = (b + 1)*x == 0 mod a
int x = a / gc;
int mx;
if ((int)2e18 / x < b) {
mx = (int)2e18;
} else
mx = x * b;
VII vals;
for (int i = 0; i < n; i++) {
int x, y;
cin >> x >> y;
vals.PB(MP(x, y));
}
for (int i = 0; i < n; i++) {
int to = (vals[i].x / mx + 1) * mx - 1;
if (vals[i].y <= to) {
vals[i].x %= mx;
vals[i].y %= mx;
continue;
} else {
vals.PB({0, vals[i].y % mx});
vals[i].y = to;
vals[i].y %= mx;
vals[i].x %= mx;
}
// vals[i].y = min(vals[i].y, (vals[i].x / mx + 1) * mx - 1);
// vals[i].x %= mx;
// vals[i].y %= mx;
}
int ret = 0;
sort(all(vals));
int mxx = -1;
for (int i = 0; i < sz(vals); i++) {
// from mxx -> vals[i].y - mxx -> vals[i].x
ret += vals[i].y - vals[i].x + 1;
ret -= min(vals[i].y - vals[i].x + 1, max(0ll, mxx - vals[i].x + 1));
mxx = max(mxx, vals[i].y);
}
cout << ret << '\n';
return 0;
}
