#pragma GCC optimize("trapv")
#include<bits/stdc++.h>
#define pb push_back
#define all(x) x.begin(), x.end()
using namespace std;
using ll = long long;
using vi = vector<ll>;
using pi = pair<ll, ll>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll n, a, b, s = 0, c;
vector<pi> seg;
ll solve1() {
set<pair<int, int>> have;
for(auto &i : seg) {
for(int j = i.first; j <= i.second; j++) {
have.insert({j%b, (j + j/b)%a});
}
}
int ans = 0;
for(auto &i : have)
ans++;
return ans;
}
ll solve2() {
return min(s, c);
}
ll solve() {
vector<pair<ll, ll>> a;
for(auto i : seg) {
if(i.second-i.first+1>=c) return c;
ll x = i.first%c, y = i.second%c;
// cout << x << " " << y << "\n";
if(x<=y) {
a.pb({x, 1});
a.pb({y+1, 0});
// cout << x << " " << y+1 << ")\n";
} else {
a.pb({0, 1});
a.pb({y+1, 0});
a.pb({x, 1});
a.pb({c, 0});
}
}
sort(all(a));
ll ans = 0, op = 0;
for(int i = 0; i +1 < a.size(); i++) {
op += (a[i].second?1:-1);
if(op) ans += a[i+1].first-a[i].first;
// cout << a[i].first << " " << a[i].second << "\n";// << op << " " << ans << "\n";
}
return ans;
}
void tst() {
for(int i = 0; i < 100; i++) {
int l = rng()%100000, r = l + (rng()%100000);
n = 1, a = rng()%100000, b = rng()%100000;
seg = {{l, r}};
s = r-l+1;
assert(solve1()==solve());
// cout << solve1() << " " << solve2() << "\n";
}
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> a >> b;
seg.resize(n);
for(auto &i : seg) {
cin >> i.first >> i.second;
s += i.second-i.first+1;
}
if((a/__gcd(a, b)) > 2000000000000000000/b) return cout << s, 0;
c = b*(a/__gcd(a, b+1));
return cout << solve(), 0;
if(s<=1000000) return cout << solve1(), 0;
if(n==1) return cout << solve2(), 0;
}
