#include <bits/stdc++.h>
using namespace std;
bool will_overflow(long long a, long long b) {
long long c = a * b;
if (a != c / b) {
return true;
}
return false;
}
long long gcd(long long a, long long b) {
while (b) {
long long c = a % b;
a = b;
b = c;
}
return a;
}
int main() {
cin.tie(nullptr)->ios_base::sync_with_stdio(false);
long long n, a, b;
cin >> n >> a >> b;
long long p = 0;
if (will_overflow(a / gcd(a, b + 1), b)) {
p = 4e18 + 1;
}
else {
p = a / gcd(a, b + 1) * b;
}
map<long long, long long> wh;
auto update = [&](long long st, long long dr) {
wh[st]++;
wh[dr + 1]--;
};
for (long long i = 1; i <= n; ++i) {
long long st, dr;
cin >> st >> dr;
long long lg = (dr - st) + 1;
st %= p;
if (st + lg - 1 < p) {
update(st, st + lg - 1);
}
else {
update(st, p - 1);
lg -= (p - st);
st = 0;
if (st + lg - 1 < p) {
update(st, st + lg - 1);
}
else {
cout << p << '\n';
return 0;
}
}
}
long long ans = 0;
long long s = 0;
for (map<long long, long long>::iterator i = wh.begin(); i != prev(wh.end()); ++i) {
s += i->second;
long long st = i->first, dr = next(i)->first - 1;
if (s) {
ans += dr - st + 1;
}
}
cout << ans;
}
