def main():

    a, b, n = list(map(int, input().split()))

    x = min(b-1, n)

    print(((a*x)//b-a*(x//b)))



if __name__ == "__main__":

    main()
def main():

    a, b, n = list(map(int, input().split()))

    x = min(b-1, n)

    print((a*x//b - a*(x//b)))



if __name__ == "__main__":

    main()
def main():
    a, b, n = list(map(int, input().split()))
    x = min(b - 1, n)
    print(((a * x) // b - a * (x // b)))


if __name__ == "__main__":
    main()

def main():
    a, b, n = list(map(int, input().split()))
    x = min(b - 1, n)
    print((a * x // b - a * (x // b)))


if __name__ == "__main__":
    main()

-    print(((a * x) // b - a * (x // b))) +    print((a * x // b - a * (x // b)))