Help me in solving BLDST problem

help
,
1

My issue

My code

#include <iostream>
#include <algorithm>
using namespace std;

int main() {
	// your code goes here
	int t;
	cin >> t;
	while (t--){
	    int n,m, count = 0;
	    float sum = 0;
	    cin >> n >> m;
	    int a[m];
	    for(int i = 0; i<m; i++){
	        cin >> a[i];
	        sum+=a[i];
	    }
	    sort(a, a+m);
	    for(int i = 0; i<a[0]; i++){
	        if (float(sum/n)>m-1){ 
	            sum = sum-m;
	            n--;
	            count++;
	        }
	        else{
	            break;
	        }
	    }
	    cout << count << endl;
	}
	return 0;
}

Problem Link: BLDST Problem - CodeChef