#include <bits/stdc++.h>

using namespace std;

int main() {
  int x,a,y,b,l;
  pair<int,int> dp[505][505];
  while (cin >> x >> a >> y >> b >> l) {
    int ll = min(a,b), rr = (a*x + b*y)/l;
    while (ll < rr) {
      int mm = (ll+rr+1)/2;
      int onea = (mm+a-1)/a;
      int oneb = (mm+b-1)/b;
      for (int i = 0; i <= y; i++) {
        dp[0][i] = make_pair(i/oneb, i%oneb);
      }
      for (int i = 1; i <= x; i++) {
        dp[i][0] = make_pair(i/onea, i%onea);
        for (int j = 1; j <= y; j++) {
          dp[i][j] = max(dp[i][j-1], dp[i-1][j]);
          if (dp[i][j-1].second+b < mm) {
            dp[i][j] = max(dp[i][j], make_pair(dp[i][j-1].first, dp[i][j-1].second+b));
          } else {
            dp[i][j] = max(dp[i][j], make_pair(dp[i][j-1].first+1, 0));
          }
          if (dp[i-1][j].second+a < mm) {
            dp[i][j] = max(dp[i][j], make_pair(dp[i-1][j].first, dp[i-1][j].second+a));
          } else {
            dp[i][j] = max(dp[i][j], make_pair(dp[i-1][j].first+1, 0));
          }
        }
      }
      if (dp[x][y].first >= l) {
        ll = mm;
      } else {
        rr = mm-1;
      }
    }
    cout << ll << endl;
  }
  return 0;
}