Help me in solving DESTBRIDGE2 problem

help
,
1

My issue

can u explain me third test case that how the answer is coming 4?

My code

#include<bits/stdc++.h>
#include<unordered_set>
using namespace std;
#define ll long long
#define ld long double
#define endl '\n'

void tc(){
  int n;ll c, sum=0;cin>>n>>c;
  int a[100];
  // vector<ll> vec;
  for(int i=0; i<n; i++){
    cin>>a[i];sum+=a[i];
  }
  sort(a, a+n);
  // for(int i=0; i<n; i++)cout<<a[i]<<" ";
  // cout<<endl<<sum<<endl;
  int ans=0;
  for(int i=0; i<n-1; i++){
    sum-=a[i];
    c-=(a[i]*sum);
    if(c<0)break;
    ans++;
  }
  cout<<n-ans;
}

int main(){

  ios_base::sync_with_stdio(false);
  cin.tie(NULL);cout.tie(NULL);

    int t;
    cin>>t;
    while(t>0){
      t--;
      tc();
     cout<<endl;
    }

  return 0;
}

Problem Link: Destroying Bridges Part 2 Practice Coding Problem

2

35 15 10 25 10 5
(5+10)*(10+15+25+35)=1275
this means we can cut 2 island from island 1
ans=6-2;