Problem:
Score : 400 points

Problem Statement

Given are integers A, B, and N.

Find the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N.

Here floor(t) denotes the greatest integer not greater than the real number t.

Constraints

1 ≤ A ≤ 10^{6}

1 ≤ B ≤ 10^{12}

1 ≤ N ≤ 10^{12}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B N

Output

Print the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N, as an integer.

Sample Input 1

5 7 4

Sample Output 1

2

When x=3, floor(Ax/B)-A×floor(x/B) = floor(15/7) - 5×floor(3/7) = 2. This is the maximum value possible.

Sample Input 2

11 10 9

Sample Output 2

9

Solution in C++ (GCC 9.2.1) (judge verdict: Wrong Answer)

//D問題//
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i,n) for(long long i=0;i<(long long)(n);i++)


int main(){
   ll A,B,N;
   cin >> A >> B >> N;

   ll a=B/N;

   if(a>0){
       cout << A*N/B-A*(N/B) << endl;
   } 
   else if(a<=0){
       cout << (A*(B-1))/B << endl;
   }

}