//# pragma GCC optimize("Ofast,no-stack-protector")
//# pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
# pragma GCC optimize("Ofast")
# pragma GCC optimization ("unroll-loops")
# include "bits/stdc++.h"
std::pair<int,int> DR[] = {{-1,0},{0,1},{1,0},{0,-1},{-1,1},{-1,-1},{1,1},{1,-1}};
# define ll long long
# define clock (clock() * 1000.0 / CLOCKS_PER_SEC)
# define rc(s) return cout << s,0
# define rcg(s) cout << s;exit(0)
# define _ ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
# define db(x) cerr << #x << " = " << x << '\n'
# define pb push_back
# define mp make_pair
# define all(s) s.begin(),s.end()
# define sz(x) (int)((x).size())
# define int ll
using namespace std;
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# define LOCAL
# define sim template < class c
# define ris return * this
# define dor > debug & operator <<
# define eni(x) sim > typename \
enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; };
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
~debug() { cerr << endl; }
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i)); }
sim, class b dor(pair < b, c > d) {
ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
*this << "[";
for (auto it = d.b; it != d.e; ++it)
*this << ", " + 2 * (it == d.b) << *it;
ris << "]";
}
#else
sim dor(const c&) { ris; }
#endif
};
#define show(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
int gcd(int a, int b)
{
if(b) return gcd(b,a%b);
return a;
}mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bool B = 1;
int n,a,b,l[1 << 20],r[1 << 20],cnt,ans;
map<int,int>m;
int32_t main(){_
//freopen("input","r",stdin);
cin >> n >> a >> b;
a /= gcd(a,b + 1);
int BIGSHAQ = 1e18;
if(BIGSHAQ / a < b) B = 0;
else a *= b;
for(int i = 1;i <= n;i++)
{
cin >> l[i] >> r[i];
cnt += r[i] - l[i] + 1;
}
if(!B) rc(cnt);
for(int i = 1;i <= n;i++)
{
if(r[i] - l[i] + 1 >= a) rc(a);
r[i] %= a;
l[i] %= a;
if(r[i] < l[i])
{
m[l[i]]++;
m[a]--;
m[0]++;
m[r[i] + 1]--;
}
else
{
m[l[i]]++;
m[r[i] + 1]--;
}
}
int lstr = 0;
int x = 0;
ans = a;
for(auto it : m)
{
if(x == 0) ans -= it.first - lstr;
x += it.second;
if(x == 0) lstr = it.first;
}
if(x == 0) ans -= a - lstr;
rc(ans);
return 0;
}
