uva 10815 - Andy's First Dictionary

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1756

好简单的一道题，居然一直runtime erro，么办法咯

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<sstream>
using namespace std;
vector<string> words;
int main(){
    string l;
    vector<string>::iterator it;
    while(getline(cin,l)){
        for(int i=0;i<l.size();i++){
            if(isupper(l[i]))
                l[i]+=32;
        }
        istringstream iss(l);        
        for(string temp;iss>>temp;){
            int len=0;
            while(len<temp.size()){
                if(isalpha(temp[len])){
                    len++;
                    continue;
                }
                temp.erase(len);
            }
            if(temp.empty())
                continue;
            it=find(words.begin(),words.end(),temp);
            if(it==words.end())
                words.push_back(temp);
        }
        //iss.clear();
    }
    sort(words.begin(),words.end());    
    for(int i=0;i<words.size();i++)
        cout<<words[i]<<endl;
    //system("pause");
}