#include <bits/stdc++.h>
#define GOOD_LUCK ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define int long long
#define endl "\n"
#define ff first
#define ss second
#define pb push_back
#define all(v) v.begin(), v.end()
using namespace std;
constexpr int MAX = 2e+5 + 1, INF = 2e+16, MOD = 1e+9 + 7, K = 31;
void _() {
int n, a, b;
cin >> n >> a >> b;
double x1 = 1. * a / gcd(a, b + 1);
double x2 = log10(1. * b);
x1 = log10(x1);
if (x1 + x2 > 18.) {
cout << 0;
return;
}
int x = a / gcd(a, b+1) * b;
set <pair<int,int>> s;
for (int i = 0; i < n; i++) {
int l, r;
cin >> l >> r;
if (r - l + 1 > x) {
cout << x;
return;
}
r %=x;
l %= x;
if (l <= r) s.insert({l, r});
if (l > r) {
s.insert({l, x-1});
s.insert({0, r});
}
}
int res=0;
while (!s.empty()) {
auto f = *s.begin();
if (s.size() == 1) {
res += f.ss - f.ff + 1;
break;
}
auto it = s.begin();
++it;
auto f1 = *it;
if (f.ss < f1.ff) {
res += f.ss - f.ff + 1;
s.erase(s.begin());
continue;
}
s.erase(s.begin());
s.erase(s.begin());
s.insert({f.ff, max(f.ss, f1.ss)});
}
cout << res;
}
signed main() {
GOOD_LUCK
int tests=1;
// cin >> tests;
for (int i=1; i <= tests; i++) {
_();
cout << endl;
}
return 0;
}
