codeforces 689C Mike and Chocolate Thieves

codeforces 689C Mike and Chocolate Thieves

​​ C. Mike and Chocolate Thieves time limit per test 2 seconds

memory limit per test 256 megabytes

input standard input

output standard output

Bad news came to Mike’s village, some thieves stole a bunch of chocolates from the local factory! Horrible!

Aside from loving sweet things, thieves from this area are known to be very greedy. So after a thief takes his number of chocolates for himself, the next thief will take exactly k times more than the previous one. The value of k (k > 1) is a secret integer known only to them. It is also known that each thief’s bag can carry at most n chocolates (if they intend to take more, the deal is cancelled) and that there were exactly four thieves involved.

Sadly, only the thieves know the value of n, but rumours say that the numbers of ways they could have taken the chocolates (for a fixed n, but not fixed k) is m. Two ways are considered different if one of the thieves (they should be numbered in the order they take chocolates) took different number of chocolates in them.

Mike want to track the thieves down, so he wants to know what their bags are and value of n will help him in that. Please find the smallest possible value of n or tell him that the rumors are false and there is no such n.

Input The single line of input contains the integer m (1 ≤ m ≤ 1015) — the number of ways the thieves might steal the chocolates, as rumours say.

Output Print the only integer n — the maximum amount of chocolates that thieves’ bags can carry. If there are more than one n satisfying the rumors, print the smallest one.

If there is no such n for a false-rumoured m, print  - 1.

Examples Input 1 Output 8 Input 8 Output 54 Input 10 Output -1 Note In the first sample case the smallest n that leads to exactly one way of stealing chocolates is n = 8, whereas the amounts of stealed chocolates are (1, 2, 4, 8) (the number of chocolates stolen by each of the thieves).

In the second sample case the smallest n that leads to exactly 8 ways is n = 54 with the possibilities: (1, 2, 4, 8),  (1, 3, 9, 27),  (2, 4, 8, 16),  (2, 6, 18, 54),  (3, 6, 12, 24),  (4, 8, 16, 32),  (5, 10, 20, 40),  (6, 12, 24, 48).

There is no n leading to exactly 10 ways of stealing chocolates in the third sample case.

二分答案 然后去验证即可

题意：一共有确切的四个窃贼 每个人都要求拿前一个人的确切的k倍 假设 第一个人拿了x

那么最后一个人一定是k^3*x 所以我每次二分一个答案 然后枚举k可以o(1)求出针对每个k 的x的个数

验证即可

#include#define ll long longll m;inline ll check(ll x){ ll tmp=0; for (ll i=2;(i*i*i)<=x;++i) tmp+=x/(i*i*i);return tmp;}int main(){ //freopen("cf.in","r",stdin); scanf("%lld",&m); ll l=0,r=m<<3; while(l<=r){ ll mid=l+r>>1; if (check(mid)>=m) r=mid-1;else l=mid+1; } if (check(l)!=m) printf("-1");else printf("%lld",l); return 0;}

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