import sys
input = sys.stdin.readline
def read_values(): return map(int, input().split())
def read_index(): return map(lambda x: int(x) - 1, input().split())
def read_list(): return list(read_values())
import math


def calc(xx,mm,aa,bb,cc,dd):
  return aa*xx+(cc*xx+dd)//mm*bb
def dfs(nn,mm,aa,bb,cc,dd):
  if nn==0:
    return -10**100
  if nn <= 2:
    return max(calc(0,mm,aa,bb,cc,dd),calc(nn-1,mm,aa,bb,cc,dd))
  add=dd//mm*bb
  aa+=cc//mm*bb
  cc%=mm
  dd%=mm
  tmp=max(calc(0,mm,aa,bb,cc,dd),calc(nn-1,mm,aa,bb,cc,dd))
  if (aa>=0 and bb>=0) or (aa<=0 and bb<=0) or cc == 0:
    return tmp+add
  if aa >= 0:
    return max(tmp,dfs((cc*(nn-1)+dd)//mm,cc,bb,aa,mm,mm-dd-1))+add
  else:
    return max(tmp,dfs((cc*(nn-1)+dd)//mm,cc,bb,aa,mm,mm-dd-1)+aa+bb)+add
  
def main():
  # n,m,a,b,c,d=read_values()
  # print(dfs(n,m,a,b,c,d))
  # return
  d,a,b,k=read_values()
  l=0
  r=10**100
  g=math.gcd(d,a)
  d//=g
  a//=g
  while l+1<r:
    m=(l+r)//2
    res=dfs(m,a,b,-((a*b)//d),d,0)
    if res<=k*b:
      l=m
    else:
      r=m
  if r==10**100:
    print(-1)
    return
  print(l*d*g)

      
if __name__ == "__main__":
  t=int(input())
  for _ in range(t):
    main()