#include <bits/stdc++.h>
// author: aykhn
using namespace std;
typedef long long ll;
#define TC int t; cin >> t; while (t--) _();
#define OPT ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define all(v) v.begin(), v.end()
#define pii pair<int, int>
#define mpr make_pair
#define eb emplace_back
#define new int32_t
#define pb push_back
#define ts to_string
#define fi first
#define se second
#define int ll
#define ins insert
#define inf 0x3F3F3F3F
#define infll 0x3F3F3F3F3F3F3F3FLL
#define bpc __builtin_popcount
__int128 n, a, b;
/*int x(int i)
{
return (i + i/b) % a;
}
int y(int i)
{
return i % b;
}*/
__int128 read() {
__int128 x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9') {
if (ch == '-') f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
x = x * 10 + ch - '0';
ch = getchar();
}
return x * f;
}
void print(__int128 x) {
if (x < 0) {
putchar('-');
x = -x;
}
if (x > 9) print(x / 10);
putchar(x % 10 + '0');
}
bool cmp(__int128 x, __int128 y) { return x >= y; }
new main()
{
n = read();
a = read();
b = read();
__int128 x = a/__gcd(a, b + 1) * b;
set<pair<__int128, __int128>> s;
for (__int128 i = 0; i < n; i++)
{
__int128 a, b;
a = read();
b = read();
if (b - a + 1 >= x)
{
s.ins(mpr(1, x));
}
else
{
__int128 l = a % x + 1;
__int128 r = b % x + 1;
if (l <= r)
{
s.ins(mpr(l, r));
}
else
{
s.ins(mpr(l, x));
s.ins(mpr(1, r));
}
}
}
set<pair<__int128, __int128>> nw;
while (s.size() > 1)
{
auto it = s.begin();
pair<__int128, __int128> a = *it;
it++;
pair<__int128, __int128> b = *it;
if (max(a.fi, b.fi) <= min(a.se, b.se))
{
s.erase(s.begin());
s.erase(s.begin());
s.ins(mpr(min(a.fi, b.fi), max(a.se, b.se)));
}
else
{
s.erase(s.begin());
nw.ins(a);
}
}
nw.ins(*s.begin());
__int128 res = 0;
for (pii a : nw)
{
res += a.se - a.fi + 1;
}
print(res);
return 0;
}
