#include <bits/stdc++.h>
#define ll long long
#define lll __int128
#define endl "\n"
using namespace std;
ll gcd(ll a, ll b) {
return b == 0 ? a : gcd(b, a % b);
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
ll n, a, b;
cin >> n >> a >> b;
/*
for(int i = 1; i <= n; ++i) {
ll l, r;
cin >> l >> r;
for(int j = l; j <= r; ++j) {
cout << (j + j / b) % a << " " << j % b << endl;
}
}
*/
//return 0;
// a or b has certain pattern
// ab -> 1 cycle, no duplikat
// next cycle: sama persis
// maintain cycles in terms of ab, merge all segments
// find modulo ab
// exist more than one cycle long -> all possible
// size ab berarti diff >= ab - 1
vector<pair<lll, int>> sweep;
ll ans = -1;
lll tot;
if(a == b + 1)
tot = b;
else
tot = (lll)a * b / gcd(a, b + 1);
set<pair<ll, ll>> s;
// t + floor(t/b)
// every a * b reset (pasti)
//for(int j = 0; j <= a * b; ++j)
// s.insert(make_pair((ll)(j + j / b) % a, (ll)j % b));
//cout << s.size() << " " << (ll)tot << endl;
for(int i = 1; i <= n; ++i) {
ll l, r;
cin >> l >> r;
if(r - l >= tot - 1) {
ans = tot;
}
else {
if(tot <= 1e18) {
l = (l % tot);
r = (r % tot);
}
if(l <= r) {
sweep.push_back(make_pair(l, 0));
sweep.push_back(make_pair(r, 1));
}
else {
sweep.push_back(make_pair(l, 0));
sweep.push_back(make_pair(tot - 1, 1));
sweep.push_back(make_pair(0, 0));
sweep.push_back(make_pair(r, 1));
}
}
}
if(ans != -1)
cout << ans << endl, exit(0);
sort(sweep.begin(), sweep.end());
int cnt = 0;
ll st = -5;
ans = 0;
for(auto i : sweep) {
if(i.second) {
// end
--cnt;
if(cnt == 0)
ans += i.first - st;
}
else {
// start
// start itu + cnt
// set start kalo belum di set
if(cnt == 0)
st = i.first - 1;
++cnt;
}
}
cout << ans << endl;
}
