#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, U b) {
  if (a < b) a = b;
}
template <typename T>
inline void gn(T &first) {
  char c, sg = 0;
  while (c = getchar(), (c > '9' || c < '0') && c != '-')
    ;
  for ((c == '-' ? sg = 1, c = getchar() : 0), first = 0; c >= '0' && c <= '9';
       c = getchar())
    first = (first << 1) + (first << 3) + c - '0';
  if (sg) first = -first;
}
template <class T, class T1>
inline void gn(T &first, T1 &second) {
  gn(first);
  gn(second);
}
template <class T, class T1, class T2>
inline void gn(T &first, T1 &second, T2 &z) {
  gn(first);
  gn(second);
  gn(z);
}
template <typename T>
inline void print(T first) {
  if (first < 0) {
    putchar('-');
    return print(-first);
  }
  if (first < 10) {
    putchar('0' + first);
    return;
  }
  print(first / 10);
  putchar(first % 10 + '0');
}
template <typename T>
inline void println(T first) {
  print(first), putchar('\n');
}
template <typename T>
inline void printsp(T first) {
  print(first), putchar(' ');
}
template <class T, class T1>
inline void print(T first, T1 second) {
  printsp(first), println(second);
}
template <class T, class T1, class T2>
inline void print(T first, T1 second, T2 z) {
  printsp(first), printsp(second), println(z);
}
int power(int a, int b, int m, int ans = 1) {
  for (; b; b >>= 1, a = 1LL * a * a % m)
    if (b & 1) ans = 1LL * ans * a % m;
  return ans;
}
long long a[100100], sum[100100], arr[100100];
int nn;
int B[100100];
void update(int u) {
  while (u <= nn) {
    B[u]++;
    u += u & -u;
  }
}
int calc(int u) {
  int ans = 0;
  while (u) {
    ans += B[u];
    u -= u & -u;
  }
  return ans;
}
int main() {
  int n;
  long long k;
  gn(n, k);
  for (int i = 1; i <= n; i++) gn(a[i]), arr[i] = sum[i] = sum[i - 1] + a[i];
  sort(arr, arr + n + 1);
  nn = unique(arr, arr + n + 1) - arr;
  long long st = -0x3f3f3f3f3f3f3f3fLL, ed = 0x3f3f3f3f3f3f3f3fLL, mid;
  while (ed - st > 1) {
    mid = st + ed >> 1;
    for (int i = 1; i <= nn; i++) B[i] = 0;
    long long tot = 0;
    update(upper_bound(arr, arr + nn, 0) - arr);
    for (int i = 1; i <= n; i++) {
      int id = upper_bound(arr, arr + nn, sum[i] - mid) - arr;
      tot += calc(id);
      update(upper_bound(arr, arr + nn, sum[i]) - arr);
    }
    if (tot >= k)
      st = mid;
    else
      ed = mid;
  }
  println(st);
  return 0;
}
