fn run() {
    input! {
        n: usize,
        k: usize,
        a: [u64; n],
    }
    let can = |m: u64| -> bool {
        let mut s = 0;
        let mut x = 0;
        let mut next = vec![0; n];
        for (i, next) in next.iter_mut().enumerate() {
            while s < m {
                s += a[x];
                x += 1;
                if x >= n {
                    x -= n;
                }
            }
            *next = x;
            s -= a[i];
        }
        let mut dp = (0..n).map(|i| (0, i)).collect::<Vec<_>>();
        for i in 0..n {
            let (v, k) = dp[i];
            let x = next[i];
            if dp[x].0 < v + 1 {
                dp[x] = (v + 1, k);
            } else if dp[x].0 == v + 1 && dp[x].1 < k {
                dp[x].1 = k;
            }
        }
        dp.iter().enumerate().any(|(i, dp)| dp.0 > k || (dp.0 == k && i <= dp.1))
    };
    let mut ok = 1;
    let mut ng = a.iter().sum::<u64>() + 1;
    while ng - ok > 1 {
        let mid = (ok + ng) / 2;
        if can(mid) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    println!("{}", ok);
}

fn main() {
    run();
}

// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------