a, b, c = map(int, input().split())
# an-b = c
# an = c
no_ans = True
if c <= b and c % a == 0:
    print(c // a)
    no_ans = False
if (b + c) % a == 0:
    print((b + c) // a)
    no_ans = False
if no_ans:
    print(-1)