993 992 991
 100 1 10
 960 935 994
 99 8 99
 60 16 1
 759 10 258
 24 19 9
 196 169 144
 1000 999 1
 945 812 917
 1000 100 10
 500 300 300
 888 777 1000
 2 1 4
 24 12 12
 767 2 514
 2 1 2
 1000 1 1
 5 2 1
 70 32 1
 765 123 899
 17 7 10
 5 4 10
 888 777 888
 66 38 4
 1000 999 1000
 9 3 300
 244 87 4
 765 123 45
 1000 1 1000
 305 203 421
 100 10 1
 64 12 8
 894 1 999
 2 1 1
 18 14 10
 6 2 4
 888 777 1
 27 26 1
 2 1 3
 5 1 5
 7 3 200
 561 31 917
 17 10 7
 93 74 831

1
 990
 27
 1127
 3
 19325
 3
 24
 1
 151
 90
 200
 143
 4
 12
 196605
 2
 999
 2
 2
 4693
 15
 3
 127
 3
 2
 600
 8
 235
 999000
 212
 9
 35
 892107
 1
 3
 8
 1
 1
 3
 20
 267
 15678
 5
 214

import java.io.*;
import java.util.*;

public class CodeForces {

	public void solve() throws IOException {
		int a = nextInt();
		double b = nextDouble();
		int c = nextInt();

		int t = Math.max(0, (int) Math.ceil((a * c - b * c) / b));
		out.print(t);
	}

	private String checkMask(int i) {
		String s = String.valueOf(i);
		StringBuffer sb = new StringBuffer();
		for (int j = 0; j < s.length(); j++) {
			if (s.charAt(j) == '4' || s.charAt(j) == '7') {
				sb.append(s.charAt(j));
			}
		}
		return sb.toString();
	}

	public static void main(String[] args) {
		new CodeForces().run();
	}

	int NOD(int a, int b) {
		while (a != 0 && b != 0) {
			if (a >= b)
				a = a % b;
			else
				b = b % a;
		}
		return a + b;
	}

	BufferedReader reader;
	StringTokenizer tokenizer;
	PrintWriter out;
	boolean isOuterFile = false;

	public void run() {
		try {
			if (isOuterFile) {
				reader = new BufferedReader(new FileReader("input.txt"));
				out = new PrintWriter(new BufferedWriter(new FileWriter(
						"output.txt")));
			} else {
				reader = new BufferedReader(new InputStreamReader(System.in));
				out = new PrintWriter(System.out);
			}

			tokenizer = null;
			// long time = new Date().getTime();
			solve();
			// out.println(time - new Date().getTime());
			reader.close();
			out.close();
		} catch (Exception e) {
			e.printStackTrace();
			System.exit(1);
		}
	}

	int nextInt() throws IOException {
		return Integer.parseInt(nextToken());
	}

	long nextLong() throws IOException {
		return Long.parseLong(nextToken());
	}

	double nextDouble() throws IOException {
		return Double.parseDouble(nextToken());
	}

	String nextToken() throws IOException {
		while (tokenizer == null || !tokenizer.hasMoreTokens()) {
			tokenizer = new StringTokenizer(reader.readLine());
		}
		return tokenizer.nextToken();
	}
}