from sys import stdin, stdout

from collections import defaultdict

import math

from queue import Queue



a, b, n = list(map(int, stdin.readline().strip().split()))



x = min(b - 1, n)



ans = math.floor(a * x / b) - a * math.floor(x / b)



stdout.writelines(str(ans) + '\n')



import math





def eq_value(a, b, x):

    return math.floor(a * x / b) - a * math.floor(x / b)





A, B, n = list(map(int, input().split()))

print((eq_value(A, B, min(B-1, n))))

from sys import stdin, stdout
from collections import defaultdict
import math
from queue import Queue

a, b, n = list(map(int, stdin.readline().strip().split()))
x = min(b - 1, n)
ans = math.floor(a * x / b) - a * math.floor(x / b)
stdout.writelines(str(ans) + "\n")

import math


def eq_value(a, b, x):
    return math.floor(a * x / b) - a * math.floor(x / b)


A, B, n = list(map(int, input().split()))
print((eq_value(A, B, min(B - 1, n))))

-from sys import stdin, stdout -from collections import defaultdict -from queue import Queue -a, b, n = list(map(int, stdin.readline().strip().split())) -x = min(b - 1, n) -ans = math.floor(a * x / b) - a * math.floor(x / b) -stdout.writelines(str(ans) + "\n") + +def eq_value(a, b, x): +    return math.floor(a * x / b) - a * math.floor(x / b) + + +A, B, n = list(map(int, input().split())) +print((eq_value(A, B, min(B - 1, n))))