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.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class LetsWatchFootball {
	public static void main(String[] args) {
		out = new PrintWriter(new BufferedOutputStream(System.out));
		Reader in = new Reader();
		double a = in.readDouble(), b = in.readDouble(), c = in.readDouble();
		out.println((int)Math.max(0, Math.ceil((a * c - b * c) / b)));
		in.close();
		out.close();
	}
	static PrintWriter out;
	static class Reader {
		BufferedReader br;
		StringTokenizer st;
		public Reader() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}
		String read() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}
		int readInt() {
			return Integer.parseInt(read());
		}
		long readLong() {
			return Long.parseLong(read());
		}
		double readDouble() {
			return Double.parseDouble(read());
		}
		char readChar() {
			return read().charAt(0);
		}
		int[] readIntArray(int n) {
			int[] a = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = readInt();
			return a;
		}
		long[] readLongArray(int n) {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = readLong();
			return a;
		}
		double[] readDoubleArray(int n) {
			double[] a = new double[n];
			for (int i = 0; i < n; i++)
				a[i] = readDouble();
			return a;
		}
		String[] readStringArray(int n) {
			String[] s = new String[n];
			for (int i = 0; i < n; i++)
				s[i] = read();
			return s;
		}
		char[] readCharArray(int n) {
			char[] ch = new char[n];
			for (int i = 0; i < n; i++)
				ch[i] = readChar();
			return ch;
		}
		String readLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
		void close() {
			try {
				br.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
}