#include <iostream>
#include <map>
#include <vector>
#include <assert.h>
#include <algorithm>
using namespace std;
map<long long int, vector<pair<long long int, long long int>>> mm;
vector<pair<long long int, long long int>> g, gg;
long long int d[3000005], aa[1000005], bb[1000005];
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
long long int n, a, b, c = 0;
cin >> n >> a >> b;
a = a / __gcd(a, b + 1);
for (int i = 1; i <= n; i++) {
long long int x, y;
cin >> x >> y;
aa[i] = x; bb[i] = y;
c += y - x + 1;
}
if (9e18 / b < a) {
cout << c;
return 0;
}
a *= b;
for (int i = 1; i <= n; i++) {
long long int x = aa[i], y = bb[i];
if (x % a <= y % a) g.push_back({x % a, y % a});
else {
g.push_back({x % a, a - 1});
g.push_back({0, y % a});
}
}
for (auto w : g) {
gg.push_back({w.first, 1});
gg.push_back({w.second + 1, -1});
}
sort(gg.begin(), gg.end());
long long int res = 0;
for (int i = 0; i < gg.size(); i++) {
d[i + 1] = d[i] + gg[i].second;
if (d[i + 1] > 0) res = res + (gg[i + 1].first - gg[i].first);
}
cout << res;
}
