Go Home (思维)

Go Home(思维）

description

There is a kangaroo at coordinate 0 on an infinite number line that runs from left to right, at time 0. During the period between time i−1 and time i, the kangaroo can either stay at his position, or perform a jump of length exactly i to the left or to the right. That is, if his coordinate at time i−1 is x, he can be at coordinate x−i, x or x+i at time i. The kangaroo's nest is at coordinate X, and he wants to travel to coordinate X as fast as possible. Find the earliest possible time to reach coordinate X.

Constraints
X is an integer.
1≤X≤10⁹

Input

The input is given from Standard Input in the following format:
X

output

Print the earliest possible time for the kangaroo to reach coordinate X.

sample input

6

sample output

3

tip

The kangaroo can reach his nest at time 3 by jumping to the right three times, which is the earliest possible time.

题解：

袋鼠在第i次跳i个单位，每次可以选择向左跳、向右跳、不跳，问最少次跳到X。

如果一直向右跳，考虑两种情况：1.恰好在第i次跳到X，这是我们最想遇到的情况。2.第i次跳过X，第i-1次没跳到X，假设在第i次跳到X+n，易知n

#include
using namespace std;
const int maxn = 44722;
int a[maxn];
int main()
{
    int n,ans;
    for(int i=1;i