#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const int INF = (int)1e9;
const long long LINF = (long long)1e18;
const long double PI = acos((long double)-1);
const long double EPS = 1e-9;
inline long long gcd(long long a, long long b) {
  long long r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
inline long long fpow(long long n, long long k, int p = MOD) {
  long long r = 1;
  for (; k; k >>= 1) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T>
inline int chkmin(T& a, const T& val) {
  return val < a ? a = val, 1 : 0;
}
template <class T>
inline int chkmax(T& a, const T& val) {
  return a < val ? a = val, 1 : 0;
}
template <class T>
inline T isqrt(T k) {
  T r = sqrt(k) + 1;
  while (r * r > k) r--;
  return r;
}
template <class T>
inline T icbrt(T k) {
  T r = cbrt(k) + 1;
  while (r * r * r > k) r--;
  return r;
}
inline void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
inline void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
inline int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
const int maxn = 300000 + 10;
int n;
long long t[maxn];
long long w[maxn];
int compare(int i, int j) {
  if (t[i] != t[j]) return t[i] > t[j];
  return i < j;
}
void solve() {
  cin >> n;
  set<pair<long long, int> > s;
  vector<int> v;
  int tot = 0;
  for (int i = (0); i < (n); i++) {
    cin >> t[i] >> w[i];
    if (i) {
      if (t[i] > t[0]) {
        s.insert(make_pair(w[i] - t[i], i));
        tot++;
      } else {
        v.push_back(i);
      }
    }
  }
  sort((v).begin(), (v).end(), compare);
  int ans = tot, ptr = 0;
  while (int((s).size())) {
    int ix = s.begin()->second;
    s.erase(s.begin());
    if (t[0] >= w[ix] - t[ix] + 1) {
      t[0] -= w[ix] - t[ix] + 1;
      tot--;
      while (ptr < int((v).size())) {
        int ix = v[ptr];
        if (t[ix] > t[0]) {
          s.insert(make_pair(w[ix] - t[ix], ix));
          ptr++, tot++;
        } else {
          break;
        }
      }
      chkmin(ans, tot);
    } else {
      break;
    }
  }
  cout << ans + 1 << "\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  solve();
  return 0;
}
