#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define ld long double
#define fi first
#define se second
ll l[1000005], r[1000005];
vector<pair<ll, ll>> v, ans;
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
/*
t = xb;
xb + x = y * a
x * (b + 1) = y * a
x = lcm(b + 1, a) / (b + 1)
a/gcd(b + 1, a) = lcm(b + 1, a) / (b + 1);
x = a/gcd(b + 1, a)
banyaknya possibility = x * b -> x = a / gcd(b + 1, a);
x * b >= r
b / x
*/
int n;
ll a, b;
cin >> n >> a >> b;
ll x = a / gcd(b + 1, a), sum = 0, ans1 = 0;
for (int i = 1; i <= n; i++) {
cin >> l[i] >> r[i];
sum += r[i] - l[i] + 1;
}
if (r[n - 1] / x < b) {
cout << sum << "\n";
return 0;
}
for (int i = 1; i <= n; i++) {
if (r[i] - l[i] + 1 >= x * b) {
cout << x * b;
return 0;
}
l[i] %= (x * b), r[i] %= (x * b);
if (l[i] <= r[i]) v.push_back({l[i], r[i]});
else v.push_back({l[i], x * b - 1}), v.push_back({0, r[i]});
}
sort(v.begin(), v.end());
for (int i = 0; i < (int)v.size(); i++) {
if (ans.empty()) {
ans.push_back(v[i]);
continue;
}
if (v[i].fi > ans.back().se) ans.push_back(v[i]);
else ans.back().se = max(ans.back().se, v[i].se);
}
for (auto u : ans) ans1 += u.se - u.fi + 1;
cout << ans1 << "\n";
}
