1 #include <bits/stdc++.h>

 2 typedef long long ll;

 3 const int maxn = 1e6+10;

 4 const ll inf = 1e18;

 5 using namespace std;

 6 ll a[maxn];

 7 ll b[maxn];

 8 ll m, n;

 9 int check(ll mid) {

10     for(ll i = 1; i <= n+1ll; ++i) {

11         b[i] = 0;

12     }

13     for(ll i = 1; i <= n; ++i) {

14         ll temp = mid/a[i];

15         if(mid%a[i]) ++temp;//所有的数必须大于等于mid

16         if(i == n && b[i] >= temp) break;//当走到n，要考虑是不是还需要往下走了

17         b[i]++;

18         if(b[i] < temp) {

19             b[i+1] += temp - b[i];

20             b[i] = temp;

21         }

22     }

23     ll cnt = 0;

24     for(ll i = 1; i <= n+1ll; ++i) {

25         cnt += b[i];

26         if(cnt > m) return 0;

27     }

28     return 1;

29

30 }

31 int main(){

32     int t;

33     scanf("%d", &t);

34     while(t--) {

35         scanf("%lld %lld", &n, &m);

36         for(ll i = 1; i <= n; ++i) {

37             scanf("%lld", a+i);

38         }

39         ll l = 1, r = inf;

40         ll ans = 0ll;

41         while(l <= r) {

42             ll mid = (l + r) / 2ll;

43             if(check(mid)) l = mid + 1ll, ans = mid;

44             else r = mid - 1ll;

45         }

46         printf("%lld\n", ans);

47     }

48

49     return 0;

50 }