Splitting an Array

#include <bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
#define vi vector<int>
#define vll vector<ll>
#define tests int t; cin >> t; while(t--)
#define pb push_back
using namespace std;

int n, k;
vll v;

bool good(ll m) {
    int i = 0, c = 0;
    while(i < n) {
        int j = i+1;
        ll s = v[i];
        if(s > m) return false;
        while(j < n && s+v[j] <= m) s += v[j++];
        i = j; c++;
    }
    return c <= k;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
    cin >> n >> k;
    v.resize(n);
    for(ll& i : v)
        cin >> i;
    ll l = 0, r = 1e15;
    while(l <= r) {
        ll m = l+(r-l)/2;
        if(good(m)) r = m-1;
        else l = m+1;
    }
    cout << l << "\n";
    return 0;
}