#include<bits/stdc++.h>

using namespace std;

using LL = long long;

const int N = 1e5 + 5;

LL c[N], ok, sum, a[N], now, n, k, l, r, mid, ans;

LL lowbit(LL x){
  return x & -x;
}

LL getsum(LL x){
  for(ans = 0; x > 0; ans += c[x], x -= lowbit(x)){
  }
  return ans;
}

void updata(int i, LL k){
  for(; i <= n; c[i] += k, i += lowbit(i)){
  }
}

bool C(LL x){
  for(int i = 1; i <= n; ++i){
    c[i] = 0;
  }
  for(int i = 1; i <= n; ++i){
    updata(i, a[i] - a[i - 1]);
  }
  sum = 0;
  for(int i = 1; i <= n; ++i){
    now = getsum(i);
    ok = max(0ll, (x - now + i - 1) / i);
    sum += ok;
    updata(i, ok * i), updata(n + 1, -ok * i);
  }
  return sum <= k;
}

int main(){
  cin >> n >> k;
  for(int i = 1; i <= n; ++i){
    cin >> a[i];
  }
  l = 0, r = (LL)(2e15);
  while(l < r){
    mid = (l + r + 1) >> 1;
    if(C(mid)){
      l = mid;
    }
    else{
      r = mid - 1;
    }
  }
  cout << l;
  return 0;
}