#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) { if(A>=N-1) { long S=0; long T=W/N; S-=T*(T+1)/2; S+=(A-(N-1))/N; cout<<S<<endl; } else if(W>0) { long S=0; long T=W/N; S-=T*(T+1)/2; S-=T+1; if(A<=T)S+=A; else S+=T; cout<<S<<endl; } else { cout<<":("<<endl; } } else { int n=W%N; long S=0; long T=W/N; S-=T*(T+1)/2; T++; S-=T; if(T*n<=A) { S+=T; A-=T*n; if(A>=N-1)S+=(A-(N-1))/N; else { S--; } } else { N=n; if(A>=N-1)S+=(A-(N-1))/N; else { S-=T+1; if(A<=T)S+=A; else S+=T; } } cout<<S<<endl; } } } }