[Silver 2] 2004번 조합 0의 개수

import java.io.*;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] arr = br.readLine().split(" ");
        int n = Integer.parseInt(arr[0]);        
        int m = Integer.parseInt(arr[1]);        

        int countTwo = count(n, 2)-count(m, 2)-count(n-m, 2);
        int countFive = count(n, 5)-count(m, 5)-count(n-m, 5);
        
        System.out.println(Math.min(countTwo, countFive));
    }
    
    public static int count(int n, int k) {
        if(n<k) { return 0; }
        int count = 0;
        
        int temp = n;
        while(temp >= k) {
            count += temp/k;
            temp = temp/k;
        }
        
        return count;
    }
}