std::string resolve(size_t len,const std::string& s,std::tr1::unordered_map<std::string,int> count){
count.clear();
if(s.length()<len) throw std::runtime_error("err");
if(s.length()==len) return s;
const size_t maxIndex=s.length()-len;
std::tr1::unordered_map<std::string,int>::iterator end=count.end();
int maxCount=1;
std::string maxStr=s.substr(0,3);
for(size_t i=1;i!=maxIndex;++i){
const std::string substr=s.substr(i,len);
std::tr1::unordered_map<std::string,int>::iterator iter=count.find(substr);
if(iter!=end){
if(++iter->second > maxCount){
maxCount=iter->second;
maxStr=substr;
}
}
else count[substr]=1;
}
return maxStr;
}
void reset(){
start=-1;
all.clear();
}