import sys

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

X=B-1

ans=(A*N)//B-A*(N//B)

if B==1:

  print((0))

  sys.exit()

while X<=N:

  ans=max(ans,(A*X)//B-A*(X//B))

  X+=B

print(ans) 
import sys

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

X=B-1

X=min(B-1,N)

ans=(A*X)//B-A*(X//B)

print(ans) 
import sys

A, B, N = list(map(int, input().split()))
X = B - 1
ans = (A * N) // B - A * (N // B)
if B == 1:
    print((0))
    sys.exit()
while X <= N:
    ans = max(ans, (A * X) // B - A * (X // B))
    X += B
print(ans)

import sys

A, B, N = list(map(int, input().split()))
X = B - 1
X = min(B - 1, N)
ans = (A * X) // B - A * (X // B)
print(ans)

-ans = (A * N) // B - A * (N // B) -if B == 1: -    print((0)) -    sys.exit() -while X <= N: -    ans = max(ans, (A * X) // B - A * (X // B)) -    X += B +X = min(B - 1, N) +ans = (A * X) // B - A * (X // B)