993 992 991
 100 1 10
 960 935 994
 99 8 99
 60 16 1
 759 10 258
 24 19 9
 196 169 144
 1000 999 1
 945 812 917
 1000 100 10
 500 300 300
 888 777 1000
 2 1 4
 24 12 12
 767 2 514
 2 1 2
 1000 1 1
 5 2 1
 70 32 1
 765 123 899
 17 7 10
 5 4 10
 888 777 888
 66 38 4
 1000 999 1000
 9 3 300
 244 87 4
 765 123 45
 1000 1 1000
 305 203 421
 100 10 1
 64 12 8
 894 1 999
 2 1 1
 18 14 10
 6 2 4
 888 777 1
 27 26 1
 2 1 3
 5 1 5
 7 3 200
 561 31 917
 17 10 7
 93 74 831

1
 990
 27
 1127
 3
 19325
 3
 24
 1
 151
 90
 200
 143
 4
 12
 196605
 2
 999
 2
 2
 4693
 15
 3
 127
 3
 2
 600
 8
 235
 999000
 212
 9
 35
 892107
 1
 3
 8
 1
 1
 3
 20
 267
 15678
 5
 214

def read_tokens():
    return input().strip().split(' ')


def read_ints():
    return [int(s) for s in read_tokens()]


# def how_many_problems(a: int, b: int, c: int):
#     l = 0
#     r = (c*a) // b
#
#     while r - l > 1:
#         m = (r + l) // 2
#         if possible(m, a, b, c):
#             l = m
#         else:
#             r = m
#
#     return l


# def possible(number_of_tasks: int, time_for_walk: int):
#     time_for_problems = sum([5*i for i in range(1, number_of_tasks+1)])
#     total_time = 4*60  # minutes
#     return (total_time - time_for_problems - time_for_walk) >= 0


def min_time_for_wait(a: int, b: int, c: int):
    l = 0
    r = (c*a) // b

    while r - l > 1:
        m = (r + l) // 2
        if possible(m, a, b, c):
            r = m
        else:
            l = m

    return r


def possible(t: int, a: int, b: int, c: int):
    total_video_data = c * a  # unit
    data_for_last_sec = (c + t) * b
    return data_for_last_sec >= total_video_data


a, b, c = read_ints()
print(min_time_for_wait(a, b, c))
