#include <bits/stdc++.h>
using i64 = long long;
#ifdef DEBUG
#include "debug.h"
#else
#define debug(...) void(23)
#endif
constexpr i64 INF = 2E18;
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
int N;
i64 A, B;
std::cin >> N >> A >> B;
std::vector<i64> L(N), R(N);
for(int i = 0; i < N; ++i) {
std::cin >> L[i] >> R[i];
}
i64 ans = 0;
for(int i = 0; i < N; ++i) {
ans += R[i] - L[i] + 1;
}
{
i64 b = B + 1;
i64 g = std::gcd(A, b);
A /= g;
}
// B * A >= INF
if(B >= (INF + A - 1) / A) {
std::cout << ans << '\n';
return 0;
}
i64 search = B * A;
debug(search);
std::vector<std::pair<i64, int>> g;
for(int i = 0; i < N; ++i) {
if(R[i] - L[i] + 1 >= search) {
std::cout << search << '\n';
return 0;
}
if(L[i] % search < (R[i] + 1) % search) {
g.emplace_back(L[i] % search, +1);
g.emplace_back((R[i] + 1) % search, -1);
} else {
g.emplace_back(L[i] % search, +1);
g.emplace_back(search, -1);
g.emplace_back(0, +1);
g.emplace_back((R[i] + 1) % search, -1);
}
}
std::sort(g.begin(), g.end());
debug(g);
i64 last = 0, nw = 0;
ans = 0;
for(auto[x, d] : g) {
if(nw > 0) {
debug(last, x);
ans += x - last;
}
nw += d;
last = x;
}
std::cout << ans << '\n';
return 0;
}
