def main():
    import sys
    input = sys.stdin.read
    data = input().split()
    
    N = int(data[0])
    K = int(data[1])
    A = list(map(int, data[2:2+N]))
    
    total = sum(A)
    low = 1
    high = total // K
    answer = 0
    
    def check(M):
        if total < M * K:
            return False
        current_sum = 0
        splits = 0
        prefix_splits = [0] * (N + 1)
        for i in range(N):
            current_sum += A[i]
            if current_sum >= M:
                splits += 1
                current_sum = 0
                prefix_splits[i + 1] = splits
            else:
                prefix_splits[i + 1] = splits
        
        if prefix_splits[N] >= K:
            return True
        
        # Compute prefix sums to quickly get suffix sums
        prefix_sum = [0] * (N + 1)
        for i in range(N):
            prefix_sum[i + 1] = prefix_sum[i] + A[i]
        
        for i in range(N):
            suffix_sum = prefix_sum[N] - prefix_sum[i]
            if suffix_sum < M:
                continue
            if prefix_splits[i] >= K - 1:
                return True
        
        return False
    
    while low <= high:
        mid = (low + high) // 2
        if check(mid):
            answer = mid
            low = mid + 1
        else:
            high = mid - 1
    
    print(answer)

if __name__ == "__main__":
    main()