#include <bits/stdc++.h>
#define nl '\n'
#ifdef LOCAL
#include "template/debug.hpp"
#else
#define dbg(...) ;
#define timer(...) ;
#endif
signed main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int n;
int64_t A, B;
std::cin >> n >> A >> B;
std::vector<int64_t> L(n), R(n);
for (int i = 0; i < n; i++) {
std::cin >> L[i] >> R[i];
}
if ((B + 1) % A == 0) {
std::vector<std::pair<int64_t, int64_t>> segs;
for (int i = 0; i < n; i++) {
if (R[i] - L[i] + 1 < B) {
auto r0 = L[i] % B;
auto r1 = R[i] % B;
if (r0 <= r1) {
segs.emplace_back(r0, r1);
} else {
segs.emplace_back(0, r1);
segs.emplace_back(r0, B - 1);
}
} else {
segs.emplace_back(0, B - 1);
}
}
std::sort(segs.begin(), segs.end());
std::vector<std::pair<int64_t, int64_t>> normalized;
for (auto [l, r] : segs) {
if (normalized.empty() || l > normalized.back().second) {
normalized.emplace_back(l, r);
} else {
normalized.back().second = r;
}
}
int64_t ans = 0;
for (auto [l, r] : normalized) {
ans += r - l + 1;
}
std::cout << ans << nl;
return 0;
}
std::vector<std::pair<int64_t, int64_t>> segs;
auto decompose = [&](int64_t t) -> std::pair<int64_t, int64_t> {
return {t % B, t / B};
};
auto process = [&](int64_t l, int64_t r) {
auto len = r - l + 1;
if (len / B >= A) {
segs.emplace_back(0, A * B - 1);
}
auto [rl, ql] = decompose(l);
auto [rr, qr] = decompose(r);
if (ql >= A) {
auto num_shift = ql / A;
ql -= num_shift * A;
qr -= num_shift * A;
}
if (qr >= A) {
segs.emplace_back(rl + ql * B, B - 1 + (A - 1) * B);
auto num_shift = qr / A;
qr -= num_shift * A;
segs.emplace_back(0, rr + qr * B);
} else {
segs.emplace_back(rl + ql * B, rr + qr * B);
}
};
for (int i = 0; i < n; i++) {
process(L[i], R[i]);
}
std::sort(segs.begin(), segs.end());
std::vector<std::pair<int64_t, int64_t>> normalized;
for (auto [l, r] : segs) {
if (normalized.empty() || l > normalized.back().second) {
normalized.emplace_back(l, r);
} else {
normalized.back().second = r;
}
}
int64_t ans = 0;
for (auto [l, r] : normalized) {
ans += r - l + 1;
}
std::cout << ans << nl;
}
