#include <bits/stdc++.h>
#define Loop(x,l,r) for (ll x = (l); x < (r); ++x)
#define LoopR(x,l,r) for (ll x = (r)-1; x >= (l); --x)
typedef long long ll;
typedef std::pair<int, int> pii;
typedef std::pair<ll , ll > pll;
using namespace std;
set<pll> s;
void add(ll l, ll r)
{
auto it = s.lower_bound(pll{l, -1});
if (it != s.begin()) {
--it;
if (it->second >= l) {
l = it->first;
auto tmp = it;
++it;
s.erase(tmp);
} else {
++it;
}
}
while (it != s.end() && r >= it->first) {
r = max(r, it->second);
auto tmp = it;
++it;
s.erase(tmp);
}
s.insert({l, r});
}
int main()
{
ll n, A, B;
cin >> n >> A >> B;
__int128 p = (__int128)A * B / __gcd(A, B+1);
if (p < LONG_LONG_MAX)
p = p * B / __gcd((ll)p, B);
Loop (i,0,n) {
ll l, r;
cin >> l >> r;
if (r - l + 1 >= p) {
l = 0;
r = p;
} else {
l %= p;
r %= p;
++r;
}
if (l < r) {
add(l, r);
} else {
add(l, p);
add(0, r);
}
}
ll ans = 0;
for (auto [x, y] : s)
ans += y - x;
cout << ans << '\n';
}
