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.Arrays;
import java.util.StringTokenizer;

public class Main {

    public static void main(String[] args) {
        try {
            (new Main()).run();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    private void run() throws IOException {
        PrintWriter out = new PrintWriter(System.out);
        FastScanner in = new FastScanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        int c = in.nextInt();
        out.println(((a - b) * c + b - 1) / b);
        out.close();
    }

    private int sumOfDigits(long n) {
        int res = 0;
        while (n > 0) {
            res += n % 10;
            n /= 10;
        }
        return res;
    }

    private class FastScanner {
        BufferedReader bufferedReader;
        StringTokenizer stringTokenizer;

        FastScanner(InputStream inputStream) {
            this.bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        }

        FastScanner(File file) throws IOException {
            this.bufferedReader = new BufferedReader(new FileReader(file));
        }

        public String next() throws IOException {
            while (stringTokenizer == null || !stringTokenizer.hasMoreTokens()) {
                String line = bufferedReader.readLine();
                if (line == null) return null;
                stringTokenizer = new StringTokenizer(line);
            }
            return stringTokenizer.nextToken();
        }

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

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

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

    }
}
