/*
use map<string,set<string> >
string substr(int start,int len) or substr(int start);
string find(char c) return index of first,or -1 if none;
cin.ignore() clear cache(such as '\n') in cin;
*/
#include<iostream>
#include<cstdlib>
#include<map>
#include<string>
#include<set>
using namespace std;
map<string,set<string> > title,author,key,publisher,year;
set<string>::iterator it;
int main(){
int i,j,n,m;
c......
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