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 Main implements Runnable {

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

        int ans = c*(a-b)/b;
        if( c*(a-b) % b != 0 ){
            ans++;
        }

        out.println( ans );
        
    }

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

    public void run() {
        try {
            in = new BufferedReader(new InputStreamReader((System.in)));
            out = new PrintWriter(System.out);

            st = null;
            rnd = new Random();

           // double start = System.currentTimeMillis();
            solve();
            //double total = (System.currentTimeMillis() - start) / 1000.0;
           // total *= 10;

            //out.println("Total time: " + total + " sec.");

            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

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

        return st.nextToken();
    }

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

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

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

    private BufferedReader in;
    private PrintWriter out;
    private StringTokenizer st;
    private Random rnd;
}