Problem:
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You are given $n$ packages of $w_i$ kg from a belt conveyor in order ($i = 0, 1, ... n-1$). You should load all packages onto $k$ trucks which have the common maximum load $P$. Each truck can load consecutive packages (more than or equals to zero) from the belt conveyor unless the total weights of the packages in the sequence does not exceed the maximum load $P$.

Write a program which reads $n$, $k$ and $w_i$, and reports the minimum value of the maximum load $P$ to load all packages from the belt conveyor.

Input

In the first line, two integers $n$ and $k$ are given separated by a space character. In the following $n$ lines, $w_i$ are given respectively.

Output

Print the minimum value of $P$ in a line.

Constraints

$1 \leq n \leq 100,000$

$1 \leq k \leq 100,000$

$1 \leq w_i \leq 10,000$

Sample Input 1

5 3
8
1
7
3
9

Sample Output 1

10

If the first truck loads two packages of $\{8, 1\}$, the second truck loads two packages of $\{7, 3\}$ and the third truck loads a package of $\{9\}$, then the minimum value of the maximum load $P$ shall be 10.

Sample Input 2

4 2
1
2
2
6

Sample Output 2

6

If the first truck loads three packages of $\{1, 2, 2\}$ and the second truck loads a package of $\{6\}$, then the minimum value of the maximum load $P$ shall be 6.

Solution in JAVA (judge verdict: Accepted)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.NoSuchElementException;

public class Main {
    static class FS {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            return hasNextByte() ? buffer[ptr++] : -1;
        }

        private boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        private void skipUnprintable() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
        }

        public boolean hasNext() {
            skipUnprintable();
            return hasNextByte();
        }

        public String next() {
            if (!hasNext()) throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public int nextInt() {
            return (int) nextLong();
        }

        public long nextLong() {
            if (!hasNext()) throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }
    }

    static int[] np;
    static int n;

    public static void main(String[] args) throws Exception {
        FS fs = new FS();
//        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
//        String s = bf.readLine();
//        int n = Integer.parseInt(s.substring(0, s.indexOf(' ')));//n packages
//        int k = Integer.parseInt(s.substring(s.indexOf(' '), s.length()));//k trucks
        n = fs.nextInt();
        int k = fs.nextInt();


        np = new int[n];
        int max = 0;
        for (int i = 0; i < n; i++) {

            np[i] = fs.nextInt();
            max = max < np[i] ? np[i] : max;
        }
        int p = 0;
        int resids = 0;

        int maxInt = 10000 *100000;
        int minInt = max-1;
        int mid = (maxInt + minInt) / 2;
        while (maxInt - minInt > 1) {
            int v = checkN(mid);
            if (v > k) minInt = mid;
            else maxInt = mid;

            mid = (maxInt + minInt) / 2;
        }
        System.out.println(maxInt);
    }

    private static int checkN(int p) {
        int resids = p;
        int ink = 1;//当前已用卡车
        for (int i = 0; i < n; i++) {
            int j = np[i];
            if (resids >= j) {
                resids -= j;
            } else {
                ink++;
                resids = p;
                i--;
            }
        }
        return ink;
    }
}