n=int(input()) nik=list(map(int,input().split())) x,y,z=input().split() x=int(x) y=int(y) z=int(z) count=0 lis=[] for i in range(0,len(nik)): if nik[i]%y==z: lis.append(nik[i]) lis.sort() k=lis[x-1] for i in range(0,len(nik)): if nik[i]==k: print(i) break