运行后，对我的输入，没有输出，为何？？？

[zhuliangsu]

运行后，对我的输入，没有输出，为何？？？
#include <iostream>
#include <string>
#include <set>

using namespace std;

typedef set<string,less<string> >str_set;

void main()
{
string name[]={"Mary","John","Ann","Joe","Ken"};

str_set s(name,name+5);

string search,upper,lower;
str_set::iterator iter;


cout<<"please input a range for searching:(Upper/Lower)\n";
cin>>upper>>lower;

for(iter=s.lower_bound(lower);iter!=s.upper_bound(upper);iter++)
cout<<*iter<<" ";//好想没执行？？？？

cout<<endl;
}