#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
typedef long long ll;
const ll mod = 1e9+7;
const int maxn = 1e6 + 5;
ll n, a, b;
ll getx(ll t) {
return (t+t/b)%a;
}
ll gety(ll t) {
return t%b;
}
ll merge(vector<pair<ll,ll>> v) {
sort(v.begin(), v.end());
// for (auto p: v) {
// cout<<p.first<<" "<<p.second<<endl;
// }
ll res = 0;
n = v.size();
auto cur = v.front();
for (int i=1; i<n; i++) {
ll x=v[i].first;
ll y=v[i].second;
if (x>cur.second) {
res += cur.second-cur.first+1;
cur = v[i];
} else {
cur.second=max(cur.second,y);
}
}
res += cur.second-cur.first+1;
return res;
}
vector<pair<ll,ll>> v;
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n>>a>>b;
v.resize(n);
for (int i=0; i<n; i++) {
cin>>v[i].first>>v[i].second;
}
auto safe_lcm = [](ll x, ll y) {
ll tmp = x / __gcd(x,y);
if (tmp > 1e18/y) return (ll)1e18 + 1;
return tmp*y;
};
ll lcm = safe_lcm(a, b + 1);
if (lcm>1e18) {
//merge intervals
ll res = merge(v);
out(res);
}
vector<pair<ll,ll>> cv;
for (int i=0; i<n; i++) {
v[i].first %= (a*b);
v[i].second %= (a*b);
if (v[i].second>=v[i].first) {
cv.push_back(v[i]);
} else {
assert(v[i].first>v[i].second);
cv.push_back({v[i].first,a*b});
cv.push_back({1,v[i].second});
}
}
ll ans = merge(cv);
out(ans);
return 0;
}
