#include <bits/stdc++.h>
using namespace std;
void itval(istream_iterator<string> it) {}
template <typename T, typename... Args>
void itval(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << endl;
  itval(++it, args...);
}
const long long int MOD = 1e9 + 7;
template <typename T>
inline void print(T x) {
  cout << x << "\n";
}
template <typename T>
inline void printvec(T x) {
  for (auto a : x) cout << a << ' ';
  cout << '\n';
}
struct custom {
  bool operator()(const pair<long long int, long long int> &p1,
                  const pair<long long int, long long int> &p2) const {
    return p1.first < p2.first;
  }
};
long long int get_pow(long long int a, long long int b, long long int M = MOD) {
  long long int res = 1;
  while (b) {
    if (b & 1) res = (res * a) % M;
    a = (a * a) % M;
    b >>= 1;
  }
  return res;
}
const long long int N = 2e5 + 5, inf = 4e18, M = 302;
void solve() {
  long long int c, p, q, a, b;
  cin >> c >> p >> q >> a >> b;
  long long int x = c / a;
  long long int ans = 0;
  for (long long int i = (long long int)max(0ll, x - 10000);
       i < (long long int)(x + 10000); i++) {
    if (i * a <= c) {
      ans = max(ans, i * p + ((c - i * a) / b) * q);
    } else
      break;
  }
  long long int y = c / b;
  for (long long int i = (long long int)max(0ll, y - 10000);
       i < (long long int)(y + 10000); i++) {
    if (i * b <= c) {
      ans = max(ans, i * q + ((c - i * b) / a) * p);
    } else
      break;
  }
  if (p * b == q * a) {
    long long int x = c / a / 2;
    for (long long int i = (long long int)max(0ll, x - 10000);
         i < (long long int)(x + 10000); i++) {
      if (i * a <= c) {
        ans = max(ans, i * p + ((c - i * a) / b) * q);
      } else
        break;
    }
    long long int y = c / b / 2;
    for (long long int i = (long long int)max(0ll, y - 10000);
         i < (long long int)(y + 10000); i++) {
      if (i * b <= c) {
        ans = max(ans, i * q + ((c - i * b) / a) * p);
      } else
        break;
    }
  }
  cout << ans << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int test = 1;
  clock_t z = clock();
  for (long long int tes = (long long int)0; tes < (long long int)(test);
       tes++) {
    solve();
  }
  fprintf(stderr, "Total Time:%.4f\n", (double)(clock() - z) / CLOCKS_PER_SEC),
      fflush(stderr);
  return 0;
}
