#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


Int W;

Int ans;
Int dfs() {
  Int C;
  int D;
  scanf("%lld%d", &C, &D);
  vector<Int> fs(D);
  for (int j = 0; j < D; ++j) {
    fs[j] = dfs();
  }
  sort(fs.begin(), fs.end());
  Int now = 0;
  for (int j = 0; j < D; ++j) {
    if (now + fs[j] <= W) {
      now += fs[j];
    } else {
      ++ans;
    }
  }
  now += C;
  ans += now / W;
  return now % W;
}

int main() {
  for (; ~scanf("%lld", &W); ) {
    ans = 0;
    const Int res = dfs();
    if (res > 0) {
      ++ans;
    }
    printf("%lld\n", ans);
  }
  return 0;
}