package main

import (
	"strconv"
	"sync"
)

type Counter struct {
	count int
	lock sync.Mutex
}

func NewCounter() *Counter {
	return &Counter{count: 0}
}

func (c *Counter) Add() {
	c.lock.Lock()
	defer c.lock.Unlock()
	c.count += 1
}

func (c *Counter) Sub() {
	c.lock.Lock()
	defer c.lock.Unlock()
	c.count -= 1
}

func (c *Counter) String() string {
	c.lock.Lock()
	defer c.lock.Unlock()
	return strconv.Itoa(c.count)
}