#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1100000;
int n, a, b, c, l[N], r[N];
vector<int> tt;
int mul(int a, int b) {
int ans = 0;
while (b) {
if (b & 1) ans = min(ans + a, (int)(1e18+1));
a = min(a + a, (int)(1e18+1));
b /= 2;
}
return ans;
}
int32_t main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n >> a >> b;
c = mul(a / gcd(a, b + 1), b);
for (int i = 1; i <= n; i++) {
cin >> l[i] >> r[i];
if (r[i] - l[i] + 1 >= c) {
cout << c;
return 0;
}
if (l[i] % c <= r[i] % c) {
tt.push_back(-(l[i] % c + 1));
tt.push_back(r[i] % c + 1);
} else {
tt.push_back(-1);
tt.push_back(r[i] % c + 1);
tt.push_back(-(l[i] % c + 1));
tt.push_back(c);
}
}
sort(begin(tt), end(tt), [&](int i, int j) {
return abs(i) < abs(j) || (abs(i) == abs(j) && i < j);
});
int ans = 0, last = -1, cnt = 0;
for (int x : tt) {
if (x > 0) {
cnt--;
if (cnt == 0)
ans += x - last + 1;
} else {
cnt++;
if (cnt == 1)
last = -x;
}
}
cout << ans;
}
