哪位大佬能帮我看一下为什么“Sleep”总是编译错误？加急！！！

#include<bits/stdc++.h>    
using namespace std;             
const int num = 10000000;          
int main(){              
freopen("data.in","r",stdin);          
int i,n,start,end;               
start = clock();
for(i=0;i<num-2;i++)
scanf("%d",&n);            
end=clock();            
printf("%f\n",double(end-start)/CLOCKS_PER_SEC); 
Sleep(5000);    
system("pause");     
return 0;          
}