#include <bits/stdc++.h>
using namespace std;
typedef double db;
typedef long long ll;
typedef long double ld;
#define int ll
typedef pair<int, int> pii;
#define endl "\n"
#define lx (id << 1)
#define rx (lx | 1)
#define all(x) (x).begin(), (x).end()
#define bit(i, mask) ((mask) >> (i) & 1)
#define foru(i,a,b) for(int i = (a); i <= (b); ++i)
#define ford(i,a,b) for(int i = (a); i >= (b); --i)
#define FastIO ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
template<typename T> bool maximize(T &res, const T &val) { if (res < val) { res = val; return true; } return false; }
template<typename T> bool minimize(T &res, const T &val) { if (val < res) { res = val; return true; } return false; }
const ll Linf = 0x3f3f3f3f3f3f3f3f;
const int Inf = 0x3f3f3f3f;
const ll Mod = 1e9 + 7;
const int Lim = 1e6 + 5;
// #define Sieve
#ifdef Sieve
vector<int> pr;
vector<int> lpf;
void Linear_sieve(int n = Lim) {
pr.assign(1, 2);
lpf.assign(n + 1, 2);
for (int x = 3; x <= n; x += 2) {
if (lpf[x] == 2) pr.push_back(lpf[x] = x);
for (int i = 1; i < pr.size() && pr[i] <= lpf[x] && pr[i] * x <= n; ++i)
lpf[pr[i] * x] = pr[i];
}
}
#endif
// #define Ckn_calc
#ifdef Ckn_calc
const int LIM = 1e6 + 16;
int fact[LIM + 10]; /// factorial: fact[n] = n!
int invs[LIM + 10]; /// inverse modular: invs[n] = n^(-1)
int tcaf[LIM + 10]; /// inverse factorial: tcaf[n] = (n!)^(-1)
void precal_nck(int n = LIM)
{
fact[0] = fact[1] = 1;
invs[0] = invs[1] = 1;
tcaf[0] = tcaf[1] = 1;
for (int i = 2; i <= n; ++i)
{
fact[i] = (1LL * fact[i - 1] * i) % Mod;
invs[i] = Mod - 1LL * (Mod / i) * invs[Mod % i] % Mod;
tcaf[i] = (1LL * tcaf[i - 1] * invs[i]) % Mod;
}
}
ll C(int n, int k) {
if (n < k || k < 0) return 0;
ll res = fact[n];
res *= tcaf[k], res %= Mod;
res *= tcaf[n - k], res %= Mod;
return res;
}
ll P(int n, int k) {
ll res = fact[n];
res *= tcaf[n - k], res %= Mod;
return res;
}
#endif
/// ====*====*====*====*====*====*====*====*====*====*====*====*====*====*====*====*====
const int base = 3;
const int N = 1e6 + 5;
const int LOG = log2(N) + 1;
const int dx[] = {+1, -1, 0, 0};
const int dy[] = {0, 0, +1, -1};
const int block = sqrt(N) + 2;
int n, a, b;
int l, r;
int mark[N];
void solve() {
cin >> n >> a >> b;
vector<pair<int, int>> seg;
foru(i, 1, n) {
cin >> l >> r;
if (l + a * b - 1 <= r)
return cout << a * b << endl, void();
l %= a * b;
r %= a * b;
if (l <= r) {
seg.push_back({l, r});
} else {
seg.push_back({0, r});
seg.push_back({l, a * b - 1});
}
}
sort(all(seg));
int last = 0;
int ans = 0;
for (auto &[l, r]: seg) {
// cout << l << " " << r << endl;
maximize(last, l);
if (last <= r)
ans += r - last + 1, last = r + 1;
}
cout << ans << endl;
}
signed main() {
FastIO;
#define task "test"
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
#ifdef Sieve
Linear_sieve();
#endif
#ifdef Ckn_calc
precal_nck();
#endif
int ntest = 1;
// cin >> ntest;
while (ntest--) {
//cout << "Case " << q << ": " << "\n";
solve();
//cout << "\n";
}
return 0;
}
/** /\_/\
* (= ._.)
* / >TL \>AC
**/
