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.*;


import java.io.*;
	import java.math.*;
	import java.awt.geom.*;
	 
	import static java.lang.Math.*;
	 
	public class Solution implements Runnable {
		
		
	    public void solve() throws Exception {
	    	
//	    	int t=sc.nextInt();
//	    	long mod=(long)1e9+7;
//	    	
//	    	while(t-->0)
//	    	{
	    		int a=sc.nextInt();
	    		int b=sc.nextInt();
	    		int c=sc.nextInt();
	    		int totaldata=a*c;
	    		if((a*c)%b==0)
	    		{
	    			out.println(Math.max(0, a*c/b-c));
	    		}
	    		else out.println( Math.max(0, a*c/b-c)+1);
	    }
	    
	    
	    static long power(long x, long y, long p) 
	    { 
	       
	        long res = 1;      
	       
	        x = x % p;  
	  
	       if (x == 0) return 0;    
	  
	        while (y > 0) 
	        { 
	            if((y & 1)==1) 
	                res = (res * x) % p; 
	            y = y >> 1;  
	            x = (x * x) % p;  
	        } 
	        return res; 
	    } 
	    
	    		
	    
	    
	    
	    
	    
	    static Throwable uncaught;
	 
	    BufferedReader in;
	    FastScanner sc;
	    PrintWriter out;
	 
	    @Override
	    public void run() {
	        try {
	            in = new BufferedReader(new InputStreamReader(System.in));
	            out = new PrintWriter(System.out);
	            sc = new FastScanner(in);
	            solve();
	        } catch (Throwable uncaught) {
	            Solution.uncaught = uncaught;
	        } finally {
	            out.close();
	        }
	    }
	 
	    public static void main(String[] args) throws Throwable {
	        Thread thread = new Thread(null, new Solution(), "", (1 << 26));
	        thread.start();
	        thread.join();
	        if (Solution.uncaught != null) {
	            throw Solution.uncaught;
	        }
	    }
	 
	}
	 
	class FastScanner {
	 
	    BufferedReader in;
	    StringTokenizer st;
	 
	    public FastScanner(BufferedReader in) {
	        this.in = in;
	    }
	 
	    public String nextToken() throws Exception {
	        while (st == null || !st.hasMoreTokens()) {
	            st = new StringTokenizer(in.readLine());
	        }
	        return st.nextToken();
	    }
	 
	    public int nextInt() throws Exception {
	        return Integer.parseInt(nextToken());
	    }
	    
	    public int[] readArray(int n) throws Exception {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		}
	 
	    public long nextLong() throws Exception {
	        return Long.parseLong(nextToken());
	    }
	 
	    public double nextDouble() throws Exception {
	        return Double.parseDouble(nextToken());
	    }
	 
	}