#include <bits/stdc++.h>
int const MAX = 1e5 + 5;
using namespace std;
bool check(long long m, long long ai, long long di, long long hm, long long am,
           long long dm) {
  long long retval;
  if (hm % (ai - dm) == 0)
    retval = m - (((hm) / (ai - dm))) * (am - (di));
  else
    retval = m - (1 + ((hm) / (ai - dm))) * (am - (di));
  if (retval > 0) return true;
  return false;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long hy, hm, ay, am, dy, dm;
  cin >> hy >> ay >> dy >> hm >> am >> dm;
  long long h, a, d;
  cin >> h >> a >> d;
  long long ans = LLONG_MAX;
  for (long long i = 0; i < 1000; i++) {
    for (long long j = 0; j < 1000; j++) {
      long long ai = ay + i;
      long long di = dy + j;
      long long c = a * i + d * j;
      if (ai <= dm) continue;
      long long l = 0, r = 10000;
      while (r - l > 1) {
        long long mid = (l + r) >> 1;
        if (check(hy + mid, ai, di, hm, am, dm))
          r = mid;
        else
          l = mid;
      }
      if (!check(hy + l, ai, di, hm, am, dm)) l++;
      if (l < 0) l = 0;
      c += l * h;
      ans = min(ans, c);
    }
  }
  cout << ans;
}
