#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define all(a) (a).begin(), (a).end()
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef long double ld;
void debug_out()
{
cerr << endl;
}
template<typename T1, typename... T2> void debug_out(T1 A, T2... B)
{
cerr << ' ' << A;
debug_out(B...);
}
#ifdef DEBUG
#define time(...) 42
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
template<typename T1, typename T2> bool chkmin(T1 &x, T2 y) { return y < x ? (x = y, true) : false; }
template<typename T1, typename T2> bool chkmax(T1 &x, T2 y) { return y > x ? (x = y, true) : false; }
signed main()
{
#ifdef DEBUG
freopen("in", "r", stdin);
#endif
ios::sync_with_stdio(0);
cin.tie(0);
int n;
ll A, B;
cin >> n >> A >> B;
ll M;
if (B % A == A - 1)
M = B;
else
{
ld temp = A * (ld)B;
if (temp > 1000000000000000100LL)
{
ll sum = 0;
while (n--)
{
ll l, r;
cin >> l >> r;
sum += r - l + 1;
}
cout << sum << '\n';
exit(0);
}
M = A * B;
}
set<ll> rem;
while (n--)
{
ll l, r;
cin >> l >> r;
for (ll x = l; x <= r; ++x)
rem.insert(x % M);
}
cout << rem.size() << '\n';
return 0;
}
