#include <bits//stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<long long, null_type, less<long long>, rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;
typedef tree<long long, null_type, less_equal<long long>, rb_tree_tag,
tree_order_statistics_node_update>
ordered_multiset;
#define ll long long
#define ld long double
#define iloop(m, h) for (auto i = m; i != h; i += (m < h ? 1 : -1))
#define jloop(m, h) for (auto j = m; j != h; j += (m < h ? 1 : -1))
#define kloop(m, h) for (auto k = m; k != h; k += (m < h ? 1 : -1))
#define lloop(m, h) for (auto l = m; l != h; l += (m < h ? 1 : -1))
#define iloop_(m, h, g) for (auto i = m; i < h; i += g)
#define jloop_(m, h, g) for (auto j = m; j < h; j += g)
#define kloop_(m, h, g) for (auto k = m; k < h; k += g)
#define lloop_(m, h, g) for (auto l = m; l < h; l += g)
#define getchar_unlocked _getchar_nolock // comment before submission
#define pll pair<ll, ll>
#define plll pair<ll, pll>
#define pllll pair<pll, pll>
#define vll vector<ll>
#define qll queue<ll>
#define dll deque<ll>
#define pqll priority_queue<ll>
#define gll greater<ll>
#define INF 1000000000000000
#define MOD1 1000000007
#define MOD2 998244353
#define MOD3 1000000009
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
set<pll> st;
void ins(pll v) {
if (!st.size()) {st.insert(v); return;}
auto it = st.upper_bound(v);
if (it != st.begin()) {
it--;
if ((*it).second >= v.first) {
v.first = min(v.first, (*it).first);
v.second = max(v.second, (*it).second);
auto it2 = it++;
st.erase(it2);
}
else it++;
}
while (it != st.end() && (*it).first <= v.second) {
v.second = max(v.second, (*it).second);
auto it2 = it++;
st.erase(it2);
}
st.insert(v);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll n, x, y;
cin >> n >> x >> y;
ll tm = __gcd(x, y+1);
ll rq = (x / tm) * y;
iloop(0, n) {
cin >> x >> y;
if (x + rq <= y + 1) {ins({0, rq-1}); break;}
x %= rq, y %= rq;
if (x <= y) ins({x, y});
else ins({x, rq-1}), ins({0, y});
}
ll cs = 0;
for (auto it : st) cs += it.second - it.first + 1;
cout << cs;
}
