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: Time Limit Exceeded)

#include<bits/stdc++.h>
#define ll long long int 
using namespace std;

int main()
{
   ios_base::sync_with_stdio(false);
   cin.tie(NULL);  
   ll a,b,n;
   cin >> a >> b >> n;
   ll max=0;ll ans=0;ll lol=0;
   for(int i=0;i<=n;i++)
   {
       ans=(a*i)/b- a*(i/b);
       if(ans > max)
       {
         max=ans;  
       }
       
   }
   cout << max << endl;
    return 0;
}