#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define mp make_pair
#define ins insert
#define btpc __builtin_popcount
#define btclz __builtin_clz
#define sz(x) (int)(x.size());
#define all(x) x.begin(), x.end()
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};
template<class X, class Y>
bool minimize(X &x, const Y &y) {
if (x > y)
{
x = y;
return true;
}
return false;
}
template<class X, class Y>
bool maximize(X &x, const Y &y) {
if (x < y)
{
x = y;
return true;
}
return false;
}
const int MOD = 1e9 + 7; //998244353
template<class X, class Y>
void add(X &x, const Y &y) {
x = (x + y);
if(x >= MOD) x -= MOD;
}
template<class X, class Y>
void sub(X &x, const Y &y) {
x = (x - y);
if(x < 0) x += MOD;
}
/* Author : Le Ngoc Bao Anh, 12A5, LQD High School for Gifted Student*/
const ll INF = 2e18;
const int N = 1e5 + 10;
ll gcd(ll a, ll b) {
if(b == 0) return a;
return gcd(b, a % b);
}
void solve() {
int n; ll A, B; cin >> n >> A >> B;
ll m = A / gcd(B + 1, A);
if(INF / m < B) m = -1;
else m = m * B;
if(m == -1) m = INF;
if(m > 1e18) {
ll ans = 0;
for(int i = 1; i <= n; i++) {
ll L, R; cin >> L >> R;
ans += R - L + 1;
}
cout << ans;
return;
}
set<pll> seg;
for(int i = 1; i <= n; i++) {
ll L, R; cin >> L >> R;
if(R - L + 1 >= m) {
cout << m;
return;
}
ll l = L % m;
if(l + (R - L) >= m) {
seg.ins(mp(l, m - 1));
L += (m - 1) - l;
L++;
seg.ins(mp(0, R - L));
} else {
seg.ins(mp(l, l + (R - L)));
}
}
ll ans = 0;
while(seg.size() > 1) {
auto iter = seg.begin();
pll x = (*iter); ++iter; pll y = (*iter);
if(x.se < y.fi) {
ans += x.se - x.fi + 1;
seg.erase(seg.begin());
} else {
seg.erase(x);
seg.erase(y);
x.fi = min(x.fi, y.fi);
x.se = max(x.se, y.se);
seg.ins(x);
}
}
if(seg.size()) {
auto iter = seg.begin();
pll x = (*iter);
ans += x.se - x.fi + 1;
}
cout << ans;
}
int main()
{
int tc = 1, ddd = 0;
// cin >> tc;
while(tc--) {
//ddd++;
//cout << "Case #" << ddd << ": ";
solve();
}
}
