Getting WA on test case 4 . The link to the question https://codeforces.net/edu/course/2/lesson/6/3/practice/contest/285083/problem/B Can anyone help? what am i doing wrong?

#include <bits/stdc++.h>
#include <stdio.h>
#define repll(i, a, n) for (lli i = a; i <= n; i++)
#define lli long long int
#define ii int, int
#define pii pair<int, int>
#define pll pair<long, long>
#define plli pair<long long int, long long int>
#define vi vector<int>
#define vvi vector<vector<int>>
#define vlli vector<long long int>
#define endl '\n'
#define fastio ios_base::sync_with_stdio(0), cout.tie(0), cin.tie(0)
using namespace std;
const int mod = 1000000007;

lli n, k, l, r, mid, ans(-1);
vlli a;

lli segments(lli target)
{
    lli cnt(0), sum(0);
    repll(i, 0, n - 1)
    {
        if (a[i] > target)
            return k + 1;
        sum += a[i];
        if (sum > target)
        {
            cnt++;
            sum = a[i];
        }
    }
    cnt++;
    return cnt;
}
void solve()
{
    cin >> n >> k;
    a.resize(n);
    
    repll(i, 0, n - 1) cin >> a[i], r += a[i];
    
    l = 0, r += 10000;
   
    while (l <= r)
    {
        mid = (l + r) / 2;
        lli seg = segments(mid);
        if (seg == k)
        {
            ans = mid;
            r = mid - 1;
        }
        else if (seg > k)
        {
            l = mid + 1;
        }
        else
            r = mid - 1;
    }
    
    cout << ans << endl;
    return;
}
int32_t main()
{
    fastio;
    int t = 1;
    while (t--)
    {
        solve();
    }
}