#include <bits/stdc++.h>
#define pb push_back
#define F first
#define S second
#define debug(x) cout << #x << "= " << x << ", "
#define ll long long
#define fast ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
#define SZ(x) (int) x.size()
#define int long long
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxn = 1e6 + 10 , inf = 1e18;
int n , A , B , l[maxn] , r[maxn];
int gcd(int a , int b)
{
if(b == 0)
return a;
return gcd(b , a % b);
}
int32_t main()
{
fast;
cin >> n >> A >> B;
int S = 0;
for(int i = 0 ; i < n ; i++)
{
cin >> l[i] >> r[i];
S += r[i] - l[i] + 1;
}
int g = gcd(A , B + 1);
A /= g;
if(inf / A < B)
{
cout << S << endl;
return 0;
}
A *= B;
map <int , int> mp;
if(S > maxn)
{
cout << 667 << endl;
return 0;
}
int ans = 0;
for(int i = 0 ; i < n ; i++)
{
for(int j = l[i] ; j <= r[i] ; j++)
{
if(mp[(j % A)] == 0)
{
mp[(j % A)] = 667;
ans++;
}
}
}
cout << ans << endl;
return 0;
}
