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 A {

	BufferedReader in;
	StringTokenizer st;
	PrintWriter out;

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

	int nextInt() throws Exception {
		return Integer.parseInt(next());
	}

	long nextLong() throws Exception {
		return Long.parseLong(next());
	}

	double nextDouble() throws Exception {
		return Double.parseDouble(next());
	}

	void solve() throws Exception {
		int a = nextInt();
		int b = nextInt();
		int t = nextInt();
		int ans = a * t - b * t + b - 1;
		ans /= b;
		if (ans < 0)
			ans = 0;
		out.println(ans);

	}

	void run() {
		try {
			Locale.setDefault(Locale.US);
			boolean oj = System.getProperty("ONLINE_JUDGE") != null;
			Reader reader = oj ? new InputStreamReader(System.in)
					: new FileReader("input.txt");
			Writer writer = oj ? new OutputStreamWriter(System.out)
					: new FileWriter("output.txt");
			in = new BufferedReader(reader);
			out = new PrintWriter(writer);
			solve();
			out.close();
		} catch (Exception e) {
			e.printStackTrace();
			System.exit(1);
		}
	}

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

	}

}
