'Sleep' was not declared in this scope

Question

报错：[Error] 'Sleep' was not declared in this scope

#include<bits/stdc++.h>
using namespace std;
int main(){
    int renshu; 
    printf("狼人杀online\n") ;//狼人杀！！！（不是真人）
    printf("请输入游戏人数："); 
    scanf("%d",&renshu);
    if (renshu > 12 || renshu < 4){
        printf("竟敢不按套路出牌，再见"); 
        return 0;
    }
    else{
        system("cls");
        system("color F");
        printf("正在加载中");
        Sleep(2000);
    }
    return 0;
}