import core.thread;
import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex;

//	Input
class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { tokens = readln.split; if (stdin.eof) throw new EOFException; } auto token = tokens[0]; tokens.popFront; return token; }
int readInt() { return to!int(readToken); }
long readLong() { return to!long(readToken); }
real readReal() { return to!real(readToken); }

//	chmin/chmax
void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

//	Pair
struct Pair(S, T) {
	S x; T y;
	int opCmp(    const Pair p) const { return (x < p.x) ? -1 : (x > p.x) ? +1 : (y < p.y) ? -1 : (y > p.y) ? +1 : 0; }
	int opCmp(ref const Pair p) const { return (x < p.x) ? -1 : (x > p.x) ? +1 : (y < p.y) ? -1 : (y > p.y) ? +1 : 0; }
	string toString() const { return "(" ~ to!string(x) ~ ", " ~ to!string(y) ~ ")"; }
}
auto pair(S, T)(inout(S) x, inout(T) y) { return Pair!(S, T)(x, y); }

//	Array
int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = as.length; for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) { return (a <  val); }); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) { return (a <= val); }); }
T[] unique(T)(in T[] as) { T[] bs; foreach (a; as) if (bs.empty || bs[$ - 1] != a) bs ~= a; return bs; }


long hp0, atk0, def0;
long hp1, atk1, def1;
long hpC, atkC, defC;

void main(string[] args) {
	try {
	for (; ; ) {
		hp0 = readLong; atk0 = readLong; def0 = readLong;
		hp1 = readLong; atk1 = readLong; def1 = readLong;
		hpC = readLong; atkC = readLong; defC = readLong;
		
		long ans = long.max;
		
		foreach (x; 0 .. 1005L) foreach (y; 0 .. 1005L) {
			const decr0 = max(0, atk1 - (def0 + y));
			const decr1 = max(0, (atk0 + x) - def1);
			if (decr1 > 0) {
				const turns = (hp1 + decr1 - 1) / decr1;
				const needed = 1 + decr0 * turns;
				long tmp;
				tmp += hpC * max(needed - hp0, 0);
				tmp += atkC * x;
				tmp += defC * y;
				chmin(ans, tmp);
			}
		}
		
		writeln(ans);
	}
	} catch (EOFException) {}
}

