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.StringTokenizer;

public class Main implements Runnable {

    void solution() throws IOException {
        int need = nextInt();
        int can = nextInt();
        int len = nextInt();
        int delta = (len*need+can-1)/can - len;
        out.println(delta);
    }

    ///////////////////// Template definitions //////////////////////////
    int nextInt() throws IOException {
        return Integer.parseInt(next());
    }

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

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

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

    public static void main(String args[]) {
        //Locale.setDefault(Locale.UK);
        new Thread(new Main()).start();
    }

    public void run() {
        try {
            boolean online = true;
            Reader reader = online
                    ? new InputStreamReader(System.in)
                    : new FileReader("my.in");
            in = new BufferedReader(reader);
            out = new PrintWriter(System.out);
            solution();
            out.flush();
            out.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(202);
        }
    }

    BufferedReader in;
    StringTokenizer st;
    PrintWriter out;
}