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 static java.util.Arrays.deepToString;

import java.io.*;
import java.util.*;

public class A {

    static void solve() throws Exception {
        int a = nextInt();
        int b = nextInt();
        int c = nextInt();
        int size = a * c;       
        int t = 0;
        while(true){            
            if((t + c) * b >= size){
                break;
            }
            t++;
        }
        System.out.print(t);
    }

    static BufferedReader br;
    static StringTokenizer st;
    static PrintWriter out;

    static void debug(Object... a) {
        System.err.println(deepToString(a));
    }

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

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

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

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

    public static void main(String[] args) {
        try {           
            br = new BufferedReader(new InputStreamReader(System.in));      
            solve();
            br.close();
        } catch (Throwable e) {
            e.printStackTrace();
            System.exit(1);
        }
    }
}