https://www.acmicpc.net/problem/1712

main.py

# BOJ 1712 손익분기점

def solve(a, b, c):
    n = c - b

    if n <= 0:
        return -1
    else:
        return a // n + 1


if __name__ == '__main__':
    a, b, c = map(int, input().split())
    print(solve(a, b, c))


# test case
def test_case1():
    assert solve(1000, 70, 170) == 11


def test_case2():
    assert solve(3, 2, 1) == -1


def test_case3():
    assert solve(2100000000, 9, 10) == 2100000001


def test_case4():
    assert solve(1, 8, 10) == 1


def test_case5():
    assert solve(100, 60, 60) == -1


def test_case6():
    assert solve(9, 60, 63) == 4