#include "bits/stdc++.h"
#define int long long
#define all(v) v.begin() , v.end()
#define sz(a) (int)a.size()
using namespace std;
const int INF = 1e18 + 5;
void _(){
int n, a, b;
cin >> n >> a >> b;
int rep = INF;
if( (a / __gcd(a, b + 1)) >= (INF + b - 1) / b) rep = INF;
else rep = (a / __gcd(a, b + 1)) * b;
vector<int> Zip, Add;
Zip.push_back(0);
Zip.push_back(rep - 1);
Zip.push_back(rep);
vector<array<int, 2>> V;
bool ok = 0;
for(int i = 1; i <= n; i++){
int l, r;
cin >> l >> r;
int gl = l % rep, gr = r % rep;
int xl = l / rep, xr = r / rep;
if(xr - xl > 1) ok = 1;
else if(xl + 1 == xr && gl <= gr) ok = 1;
V.push_back({gl, gr});
Zip.push_back(gl);
Zip.push_back(gr + 1);
}
if(ok){
cout << rep << '\n';
return;
}
sort(all(Zip));
Zip.erase(unique(all(Zip)), Zip.end());
int m = sz(Zip);
Add.assign(m, 0);
for(array<int,2> X : V){
int pl = lower_bound(all(Zip), X[0]) - Zip.begin();
int pr = lower_bound(all(Zip), X[1] + 1) - Zip.begin();
//cout << X[0] << ' ' << X[1] << '\n';
//cout << pl << ' ' << pr << '\n';
Add[pl]++;
Add[pr]--;
if(X[0] > X[1]) Add[0]++;
}
int ans = 0, cur = 0;
for(int i = 0; i + 1 < m; i++){
cur += Add[i];
if(i + 1 < m && cur > 0) ans += Zip[i + 1] - Zip[i];
}
cout << (long long) ans << '\n';
}
int32_t main(){
cin.tie(0); ios::sync_with_stdio(0);
int tc=1;//cin >> tc;
while(tc--) _();
return 0;
}
