#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];
set <pair <int , int> > st;
int gcd(int a , int b)
{
if(b == 0)
return a;
return gcd(b , a % b);
}
void add (int L , int R)
{
if(st.empty())
{
st.insert(make_pair(L , R));
return;
}
auto it = st.upper_bound({L , L});
if(it != st.begin())
it--;
auto v = *it;
if(v.S < L)
it++;
if(it == st.end())
{
st.insert({L , R});
return;
}
auto u = *it;
L = min(u.F , L);
vector <pair <int, int>> vec;
while(u.F <= R)
{
vec.pb(u);
it++;
if(it == st.end())
break;
u = *it;
}
if(!vec.empty())
{
R = max(R , vec.back().S);
}
for(auto u : vec)
st.erase(u);
st.insert({L , R});
}
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;
for(int i = 0 ; i < n ; i++)
{
int tmp = l[i] / A;
tmp = tmp * A;
l[i] -= tmp;
r[i] -= tmp;
add(l[i] , min(r[i] , A - 1));
if(r[i] >= A)
{
r[i] -= A;
add(0 , min(A - 1 , r[i]));
}
}
int ans = 0;
for(auto u : st)
{
ans += u.S - u.F + 1;
}
cout << ans << endl;
return 0;
}
