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 implements Runnable {
    private MyScanner in;
    private PrintWriter out;

    private void solve() {
        int a = in.nextInt();
        int b = in.nextInt();
        int c = in.nextInt();
        out.println(((a - b) * c + b - 1) / b);
    }

    @Override
    public void run() {
        in = new MyScanner();
        out = new PrintWriter(System.out);
        solve();
        in.close();
        out.close();
    }

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

    class MyScanner {
        private BufferedReader br;
        private StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        public void close() {
            try {
                br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public boolean hasNext() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String s = br.readLine();
                    if (s == null) {
                        return false;
                    }
                    st = new StringTokenizer(s);
                } catch (IOException e) {
                    e.printStackTrace();
                    return false;
                }
            }
            return st != null && st.hasMoreTokens();
        }

        private String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String s = br.readLine();
                    if (s == null) {
                        return null;
                    }
                    st = new StringTokenizer(s);
                } catch (IOException e) {
                    e.printStackTrace();
                    return null;
                }
            }
            return st.nextToken();
        }

        public String nextLine() {
            try {
                st = null;
                return br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }
        }

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

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

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