
int main() {
  int A,B,C,D,N,i,MAX;
  MAX = 0;
  scanf("%d %d %d ", &A, &B, &N);
  for (i=1;i<N+1;i++)
  {
      C = ((A*i)/B);
      
      D = (i/B);
      //printf("C = %d D = %d\n",C,D);

      if(MAX < (C - D)){
          MAX = C - D;
      }

  }
  printf("%d",MAX);
  return 0;
}