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

flag = False
for n in range(1, 2*10**5+1):
    ans = n*A
    if ans>B:
        if ans-B==C:
            print(n)
            flag = True
    else:
        if ans==C:
            print(n)
            flag = True

if flag==False:
    print(-1)