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