为啥就是错的，这是bug吗

public class Solution {
    public static void main(String[] args) throws Exception {
        //在此编写你的代码
        //读取三个数字
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int a = Integer.parseInt(reader.readLine());
        int b = Integer.parseInt(reader.readLine());
        int c = Integer.parseInt(reader.readLine());
        //正数和负数的计数器
        // na为正数
        int na = 0;
        // po为负数
        int po = 0;

        int zero = 0;
        if (a > 0) {
            na++;
        } else if (a == 0) {
            zero++;
        } else {
            po++;
        }

        if (b > 0) {
            na++;
        }else if (b == 0) {
            zero++;
        }else {
            po++;
        }

        if (c > 0) {
            na++;
        }else if (c == 0) {
            zero++;
        }else {
            po++;
        }
        System.out.println("负数个数：" + po);
        System.out.println("正数个数：" + na);
    }
}