Description
There are n veges stand in line, Albert_s plan to punish them since they are too weak. The picture following below shows one of the veges waiting to be kicked.

Now Albert_s plan to kick all the veges on days in order. Since Kick the vege costs him RP, and the final cost is equal to the max cost of one day on the days.

Albert_s wants to minimize the final cost, so how much RP he costs by following the rule above?

Input
The first line contains two integer ;

The second line contains space-separated integers , the elements of the array.

，
，
​

Output
A number indicating the answer.

Sample Input
5 2
2 1 3 4 5
Sample Output
9

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
using namespace std;
const int N = 1e5;

int n, k;
int a[N + 5];

bool judge(int rp)
{
    int cnt = 1;
    int sum = 0;
    for(int i = 0; i < n; ++i)
    {
        sum += a[i];
        if(sum > rp)
        {
            sum = a[i];
            cnt++;
        }
    }
    return cnt <= k;
}

int main()
{
    while(~scanf("%d%d", &n, &k))
    {
        int l = 0;
        int r = 0;
        for(int i = 0; i< n; ++i)
        {
            scanf("%d", &a[i]);
            l = max(l, a[i]);
            r += a[i];
        }
        while(l < r)
        {
            int mid = (r + l) / 2;
//            cout << judge(mid) << '\n';
            if(judge(mid))///如果中值可行，要找更小的值就把它作為右界（上限）
                r = mid;
            else
                l = mid + 1;
        }
        cout << r << '\n';
    }
    return 0;
}