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)

//17571@nith.ac.in @Ankit Verma
#include <bits/stdc++.h>
using namespace std;
#define ff          first
#define ss          second
#define pb          push_back
#define MP          make_pair
#define int         long long
#define ll          long long
#define inf         0x3f3f3f3f
#define MOD         1000000007
#define ld          long double
#define eb          emplace_back
#define pii         pair<int,int>
#define ull         unsigned long long
#define all(v)      v.begin(), v.end()
#define f(i,x,n)    for(int i=x;i<n;i++)
#define fr(i,x,n)   for(int i=x;i>=n;i--)
#define fastio      ios::sync_with_stdio(false)

void IO() {
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
}

int32_t main() {
    //IO();
    fastio;
    cin.tie(nullptr);
    cout.tie(nullptr);
    ll a, b, n; cin >> a >> b >> n;
    ll x, y;
    if (n < b) {
    	x = n - 1;
    	y = (a * x) / b - a * (x / b);
    	cout << y << endl;
    } 
    else if (n % b == 0) {
    	x = n - 1;
    	y = (a * x) / b - a * (x / b);
    	cout << y << endl;
    } 
    else {
    	x = n - 1;
    	y = (a * x) / b - a * (x / b);
    	cout << y << endl;
    }
    

    return 0;
}