#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

long long get(long long n){
	return n*(n+1)/2;
}

long long get(long long n,long long w){
	return get(w/n)*n + (w%n)*(w/n+1);	
}

int main(){
	
	int _t;
	cin>>_t;
	
	rep(_,_t){
		
		long long N,A,W,K;
		scanf("%lld %lld %lld %lld",&N,&A,&W,&K);
		
		long long ok = -1,ng = Inf;
		while(ng-ok>1){
			long long mid = (ok+ng)/2;
			
			long long cur = A;
			cur -= (mid+1) * (K-1);
			cur -= mid;
			
			if(cur<0){
				ng = mid;
			}
			else if(K!=N){
				ok = mid;
			}
			else{
				cur -= get(N,W);
				if(cur<0)ng = mid;
				else ok = mid;
			}
			
		}
		if(ok!=-1){
			cout<<ok<<endl;
			continue;
		}
		
		if(K!=N){
			if(N-K<=W){
				cout<<-1<<endl;
			}
			else{
				cout<<":("<<endl;
			}
			continue;
		}
		else{
			if(W==0){
				cout<<":("<<endl;
				continue;
			}
			assert(false);
			long long ok = W+1,ng = 0;
			
			while(ok-ng>1){
				long long mid = (ok+ng)/2;
				long long cur = W;
				cur -= mid;
				
				
				if(cur<=0)ok = mid;
				else ng = mid;
				
			}
			cout<<ok<<endl;
			
		}
		
		
	}
	
    return 0;
}