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)

#include<iostream>
#include <cmath>
using namespace std;
typedef long long ll;

ll A, B, N;

int main() {
  cin >> A >> B >> N;
  ll res = -100000000000;
  int count = 0;
    
  for (ll x = 0; x <= N; x++) {
    ll tmp = floor(A*x/B) - (A * floor(x/B));
    if (tmp == 2) {
      count++;
      if (count == 2) break;
    }
    if (tmp > res) res = tmp;
    
  }
  cout << res << endl;
}