#include<bits/stdc++.h>
#include<boost/multiprecision/cpp_int.hpp>
using namespace std;using namespace boost::multiprecision;int main(){int t;cin>>t;while(t--){cpp_int D,A,B,K,n,a,b,c,d,m,x,g,r,l=0,h,q,s,v;cin>>D>>A>>B>>K;D/=g=gcd(D,A);A/=g;if(A*B%D<1&&D*K+2>A){cout<<-1<<'\n';}else{h=A*B*K+2;while(l+1<h){x=n=(l+h)/2;a=B;b=-A*B/D;c=D;m=A;s=v=d=0;while(a+=c/m*b,c%=m,s+=d/m*b,d%=m,v=max(v,max(s,s+a*~-n+b*(q=(c*~-n+d)/m))),n=q){s+=(a+b)*(a<0);d=m+~d;swap(a,b);swap(c,m);}(v<=B*K?l:h)=x;}cout<<g*D*l<<'\n';}}}