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.util.Arrays;
import java.util.Scanner;
import static java.lang.Math.*;

public class A extends Template {

    public void run() {
        double a = d(), b = d(), c=d();
        int t = (int) Math.ceil((c*(a-b))/b);
        System.out.println(t < 0 ? 0 : t );
    }

}




















class Template {

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

    private Scanner sc = new Scanner(System.in);

    public int toi(String s) {
        return Integer.parseInt(s);
    }

    public double tod(String s) {
        return Double.parseDouble(s);
    }

    public long tol(String s) {
        return Long.parseLong(s);
    }

    public int i() {
        return sc.nextInt();
    }

    public double d() {
        return sc.nextDouble();
    }

    public String s() {
        return sc.next();
    }

    public String l() {
        return sc.nextLine();
    }

    public int[] ai() {
        String[] line = as();
        int[] ints = new int[line.length];
        for (int i = 0; i < ints.length; i++)
            ints[i] = toi(line[i]);
        return ints;
    }

    public double[] ad() {
        String[] line = as();
        double[] doubles = new double[line.length];
        for (int i = 0; i < doubles.length; i++)
            doubles[i] = tod(line[i]);
        return doubles;
    }

    public int[] al() {
        String[] line = as();
        int[] ints = new int[line.length];
        for (int i = 0; i < ints.length; i++)
            ints[i] = toi(line[i]);
        return ints;
    }

    public String[] as() {
        return l().split("[ ]+");
    }

    public int[] aof(int n, int i) {
        int a[] = new int[n];
        Arrays.fill(a, i);
        return a;
    }

}
