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 <string>
#include <math.h>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <set>
#include <queue>
#include <deque>
#include <map>
#include <stack>
using namespace std;

#define mod 1000000007
#define ten5 100005
#define ten52 200005
#define ten6 1000005
#define PI 3.1415926
#define pb(x) push_back(x)
#define all(x) x.begin(),x.end()
#define mkpr(x1,x2) make_pair(x1,x2)
typedef long long int ll;

//ll num[50];
//ll num2[50];
ll num[ten52];
//stack<char> stk;
//set<ll> sll;
//map<string,ll> mp,mp1;
//map<pair<ll,ll>,ll>::iterator iter;
//map<ll,ll> mp;
//deque<char> deq;
//vector<ll> vll;


int main(void)
{
    //double ans=0.0,d,d1,d2;
    //float f,g,h;
    long long int m,n,i,j,k=1;
    long long int a,a1,a2,a3,sum;
    //string s,s1,s2;
    //char c,c1;
    sum=a=a1=a2=a3=0;
    cin>>a1>>a2>>n;
    if(a2==1)
    {
        cout<<0;
        return 0;
    }
    if(a2>n)
        cout<<(int)floor(a1*n/a2);
    else
        cout<<a1*(int)floor((a2-1)/a2);
    return 0;
}