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.IOException;
import java.io.InputStreamReader;
import java.io.Closeable;
import java.util.Iterator;
import java.io.BufferedReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.NoSuchElementException;
import java.io.Writer;
import java.util.StringTokenizer;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 * @author Jacob Jiang
 */
public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		QuickScanner in = new QuickScanner(inputStream);
		ExtendedPrintWriter out = new ExtendedPrintWriter(outputStream);
		TaskA solver = new TaskA();
		solver.solve(1, in, out);
		out.close();
	}
}

class TaskA {
	public void solve(int testNumber, QuickScanner in, ExtendedPrintWriter out) {
        int a = in.nextInt();
        int b = in.nextInt();
        int c = in.nextInt();
        out.println(NumberUtils.upDiv(a * c, b) - c);
    }
}

class QuickScanner implements Iterator<String>, Closeable {
    BufferedReader reader;
    StringTokenizer tokenizer;
    boolean endOfFile = false;

    public QuickScanner(InputStream inputStream){
        reader = new BufferedReader(new InputStreamReader(inputStream));
        try {
            tokenizer = new StringTokenizer(reader.readLine());
        } catch (Exception e) {
            endOfFile = true;
        }
    }

    public boolean hasNext() {
        if (!tokenizer.hasMoreTokens()) {
            try {
                checkNext();
            } catch (NoSuchElementException ignored) {
            }

        }
        return !endOfFile;
    }

    private void checkNext() {
        if (endOfFile) {
            throw new NoSuchElementException();
        }
        try {
            while (!tokenizer.hasMoreTokens()) {
                tokenizer = new StringTokenizer(reader.readLine());
            }
        } catch (Exception e) {
            endOfFile = true;
            throw new NoSuchElementException();
        }
    }

    public String next() {
        checkNext();
        return tokenizer.nextToken();
    }

    public void remove() {
        throw new UnsupportedOperationException();
    }

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

    public void close() {
        try {
            reader.close();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }


}

class ExtendedPrintWriter extends PrintWriter {


    public ExtendedPrintWriter(Writer out) {
        super(out);
    }

    public ExtendedPrintWriter(Writer out, boolean autoFlush) {
        super(out, autoFlush);
    }

    public ExtendedPrintWriter(OutputStream out) {
        super(out);
    }

    public ExtendedPrintWriter(OutputStream out, boolean autoFlush) {
        super(out, autoFlush);
    }

    }

class NumberUtils {
    public static int upDiv(int a, int b) {
        return a % b == 0 ? (a / b) : (a / b + 1);
    }

    }

