#include<iostream>
using namespace std;
int T;
main()
{
	cin>>T;
	for(;T--;)
	{
		int N,A,W,K;
		cin>>N>>A>>W>>K;
		if(N>K)
		{
			if(K-1<=A)
			{
				cout<<(A-(K-1))/K<<endl;
			}
			else if(N-K+1<=W)
			{
				cout<<-1<<endl;
			}
			else
			{
				cout<<":("<<endl;
			}
		}
		else
		{
			if(W%N==0)
			{
				long S=0;
				long T=W/N;
				S-=T*(T+1)/2;
				if(A>=N-1)S+=(A-(N-1))/N;
				cout<<S<<endl;
			}
			else
			{
				int n=W%N;
				long S=0;
				long T=W/N;
				S-=T*(T+1)/2;
				T++;
				S-=T;
				if(n-1<=A)
				{
					A-=n-1;
					int a=A/n;
					if(a<T)S+=a;
					else
					{
						S+=T-1;
						A-=(T-1)*n;
						S+=A/N;
					}
				}
				cout<<S<<endl;
			}
		}
	}
}