def solve():
    A,B,C=map(int,input().split())

    flag=0
    for N in range(1,10**6):
        if A*N>B:
            M=A*N-B
        else:
            M=A*N

        if M==C:
            flag=1
            print(N)

    if not flag:
        print(-1)

#==================================================
solve()