#pragma GCC optimize("Ofast,O2,O3,unroll-loops")
#pragma GCC target("avx2")
#include <bits/stdc++.h>
using namespace std;
void debug_out() { cerr << endl; }
template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
cerr << "[" << H << "]";
debug_out(T...);
}
#ifdef dddxxz
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
#define SZ(s) ((int)s.size())
#define all(x) (x).begin(), (x).end()
#define lla(x) (x).rbegin(), (x).rend()
clock_t startTime;
double getCurrentTime() {
return (double) (clock() - startTime) / CLOCKS_PER_SEC;
}
#define MP make_pair
typedef long long ll;
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
const double eps = 0.000001;
const int MOD = 1e9 + 7;
const int INF = 1000000101;
const long long LLINF = 1223372000000000555;
const int N = 1e6 + 3e2;
const int M = 2222;
void solve(int TC) {
int n; ll a, b;
cin >> n >> a >> b;
ll x;
if (double(a) / __gcd(a, b + 1) * b > 3e18){
x = 4e18;
} else x = a / __gcd(a, b + 1) * b;
vector<pair<ll, ll>> segments;
for (int i = 1; i <= n; i++){
ll l, r;
cin >> l >> r;
if (r - l + 1 >= x){
cout << x << endl;
return;
}
l %= x, r %= x;
if (l > r){
segments.emplace_back(l, x - 1);
segments.emplace_back(0, r);
} else segments.emplace_back(l, r);
}
sort(all(segments));
ll ans = 0;
n = segments.size();
for (int i = 0; i < n;){
ll l = segments[i].first, r = segments[i].second;
int j = i;
while (j < n && segments[j].first <= r){
r = max(r, segments[j].second);
j++;
}
ans += r - l + 1;
i = j;
}
cout << ans;
}
int main() {
startTime = clock();
ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
#ifdef dddxxz
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
int TC = 1;
// cin >> TC;
for (int test = 1; test <= TC; test++) {
//debug(test);
//cout << "Case #" << test << ": ";
solve(test);
}
cerr << endl << "Time: " << int(getCurrentTime() * 1000) << " ms" << endl;
return 0;
}
