#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#define BUFSIZE 1000000
int A,B,N;
long long result = 0;
long long rem[BUFSIZE]={0};
int cal(int x){
  if(x == N + 1) return 0;

  int a=(int)(A*x/B);
  int b= (int)x/B;

  rem[x] = a - b*A;
  if(a - b*A == 0)  cal(x + 1);

  if(rem[x] >= rem[x-1])   result = rem[x];
  cal(x + 1);
}

int main(void){

  scanf("%d %d %d",&A,&B,&N);
  cal(1);
  printf("%d",result);
}
