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.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.StreamTokenizer;


public class A {
    
    public static void main(String[] args) throws Exception {
        int a = nextInt(), b = nextInt(), c = nextInt();
        
        if(b >= a)
            exit(0);
        
        int need = a*c;
        int take = (need+b-1)/b;
        
        int m = Math.max(take - c, 0);
        println(m);
    }
    
    /////////////////////////////////////////////////////////////////
    // IO
    /////////////////////////////////////////////////////////////////
    private static StreamTokenizer in;
    private static PrintWriter out;
    private static BufferedReader inB;
    
    private static boolean FILE=false;
    
    private static int nextInt() throws Exception{
        in.nextToken();
        return (int)in.nval;
    }
    
    private static String nextString() throws Exception{
        in.nextToken();
        return in.sval;
    }
    
    static{
        try {
            out = new PrintWriter(FILE ? (new FileOutputStream("output.txt")) : System.out);
            inB = new BufferedReader(new InputStreamReader(FILE ? new FileInputStream("input.txt") : System.in));
        } catch(Exception e) {e.printStackTrace();}
        in = new StreamTokenizer(inB);
    }
    /////////////////////////////////////////////////////////////////
    
    /////////////////////////////////////////////////////////////////
    // pre - written
    /////////////////////////////////////////////////////////////////
    private static void println(Object o) throws Exception {
        out.println(o);
        out.flush();
    }
    private static void exit(Object o) throws Exception {
        println(o);
        exit();
    }
    private static void exit() {
        System.exit(0);
    }
    private static final int  INF = Integer.MAX_VALUE;
    private static final int MINF = Integer.MIN_VALUE;
    //////////////////////////////////////////////////////////////////
}
