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 <bits/stdc++.h>
using namespace std;

void solve(std::istream &ist, std::ostream &ost)
{
    /* ------- 宣言と入力 ------- */

    long long A, B, N;
    ist >> A >> B >> N;

    /* ------- 計算 ------- */
    int for_count = min(A, N);

    int tmp1 = floor(A * for_count / B);
    int tmp2 = A * floor(for_count / B);
    int ans = tmp1 - tmp2;

    ost << ans << endl;
}

#ifndef WOMAIN
int main()
{
    solve(std::cin, std::cout);
    return 0;
}
#endif