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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

function Scanner(input) {
	var self = this;
	self.itemNo = 0;
	self.orgStr = input;
	self.splitedStrs = (function(target) {
		var result = [];
		var target = target.replace(/[\n \t]+/g, " ");
		var strs = target.split(" ");
		for (var i = 0, len = strs.length; i < len; i++) {
			result.push(strs[i]);
		}
		return result;
	}(input));

	self.next = function() {
		var result = self.splitedStrs[self.itemNo];
		self.itemNo++;
		return (result != null) ? result : null;
	}

	self.nextInt = function() {
		var result = self.splitedStrs[self.itemNo];
		self.itemNo++;
		return (result != null) ? parseInt(result) : null;
	}

	self.nextBigDecimal = function() {
		var result = self.splitedStrs[self.itemNo];
		self.itemNo++;
		return (result != null) ? parseFloat(result) : null;
	}
	
	self.nextByte = function() {
		var result = self.splitedStrs[self.itemNo];
		self.itemNo++;
		return (result != null) ? new Int8Array(result) : null;
	}

}

function Main(sc) {

	var A = sc.nextInt();
	var B = sc.nextInt();
	var N = sc.nextInt();
	var max = 0;
	
	if (A > B) {
		var wk = 0;
		for (var x = 0; x <= N && x <= 100000; x++) {
			wk = Math.floor((A * x)/ B) - A * Math.floor(x / B);
			if (wk > max) max = wk;
		}
	}
	else {
		var x = (N >= B) ? B - 1 : N;
		max = Math.floor((A * x)/ B) - A * Math.floor(x / B);
	}
	
	console.log(max);
}
Main(new Scanner(require("fs").readFileSync("/dev/stdin", "utf8")));
// Main(new Scanner("33"));

// var str1 = sc.next(); // Stringで取得
// var int1 = sc.nextInt(); // intで取得
// var bd1 = sc.nextBigDecimal(); // BigDecimalで取得
// var byte1 = sc.nextByte(); // byteで取得
// for (var i = 0; i < 1000000000; i++) var toDelay = "aaa"; // 1000msくらいの遅延