c++找错误

#include<iostream>
int main()
using std::cout;
using std::cin;
int x;
cout<<"请输入一个数!\n";
cout<<"x:";
cin>>x;
if(x>=1)
{
if(x==1)
cout<<"ni shu ru de shi 1\n";
else
{
if(x>100)
cout<<"shu ru l yi ge da yu 100 de shu\n";
else if(x==100)
cout<<"shu ru l yi ge deng yu 100 de shu\n";
else
cout<<"shu ru l yi ge da yu 1 xiao yu 100 de shu\n ";
}
}
else
cout<<"shu ru l yi ge xiao yu 1 de shu\n";
return 0;
哪里错了，运行时出现.如下错误
D:\c++\c语言\MSDev98\Bin\去\w.cpp(8) : error C2501: 'cin' : missing storage-class or type specifiers
D:\c++\c语言\MSDev98\Bin\去\w.cpp(8) : error C2371: 'cin' : redefinition; different basic types
d:

将 main 函数的函数体用{}括起来就能编译通过了。
#include<iostream>

int main()
{
using std::cout;
using std::cin;
int x;
cout<<"请输入一个数!\n";
cout<<"x:";
cin>>x;
if(x>=1)
{
if(x==1)
cout<<"ni shu ru de shi 1\n";
else
{
if(x>100)
cout<<"shu ru l yi ge da yu 100 de shu\n";
else if(x==100)
cout<<"shu ru l yi ge deng yu 100 de shu\n";
else
cout<<"shu ru l yi ge da yu 1 xiao yu 100 de shu\n ";
}
}
else
cout<<"shu ru l yi ge xiao yu 1 de shu\n";
return 0;
}

#include<iostream>
using std::cout;
using std::cin;
int main()
{
int x;
cout<<"请输入一个数!\n";
cout<<"x:";
cin>>x;
if(x>=1)
{