#include <bits/stdc++.h>
void Solve();
int main() { Solve(); }
using namespace std;
const int INF = 1e9;
const int N = 20;
const double e = 1E-10;
int hm, am, dm;
int check(int ay, int dy) {
  int m = max(0, ay - dm), y = max(0, am - dy);
  if (!m) return -1;
  return (hm / m + (hm % m != 0)) * y + 1;
}
void Solve() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int hy, ay, dy, h, a, d, mn = 1e9;
  cin >> hy >> ay >> dy >> hm >> am >> dm >> h >> a >> d;
  for (int i = 0; i <= 200; i++) {
    for (int j = 0; j <= 200; j++) {
      int hp = check(ay + i, dy + j);
      if (hp == -1) continue;
      mn = min(mn, max(0, hp - hy) * h + i * a + j * d);
    }
  }
  cout << mn;
}
