B. Friends and Candies

#include<stdio.h>
#include<iostream>
#include<string.h>
#include<algorithm>
#include<map>
#include<queue>
#include<math.h>
using namespace std;
#define ll long long

int a[200010];

int main()
{
    
    
	int t;
	cin>>t;
	while(t--)
	{
    
    
		int n;
		cin>>n;
		double sum = 0;
		for(int i = 1; i <= n; i++)
		{
    
    
			cin>>a[i];
			sum += a[i];
		}
		int k = 0;
		sum /= n;
		ll ans = (ll)sum;
		for(int i = 1; i <= n; i++)
		{
    
    
			if(a[i] > ans)k++;
		}
		if(sum-ans >= 0.0000001)cout<<-1<<endl;
		else cout<<k<<endl;
	}
}