代码：

#include<bits/stdc++.h>
using namespace std; 
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0); 
	cout.tie(0);
	int n;
	string a[101], b[101];
	cin >> n; 
//	cout << n << endl;
	for(int i = 0; i < n; i++) cin >> a[i] >> b[i];
	string s;
	bool flag = 0;
	int first = 0, en= 0;
	cin >> s;
	string s2 = "";
	int e = s.length();
	string s1 = s;
	for(int i = 0; i < e; i++){
        if(i == e - 1)
            en = e - 1;
//		cout << first << endl; 
	//	cout << i << " ";
		if(s1[i] >= 'a' && s1[i] <= 'z' && flag == 0){
			first = i;
			flag = 1;
			continue;
		}
		if(s1[i] >= 'a' && s1[i] <= 'z')
			continue;
	//	if(!(s1[i] >= 'a' && s1[i] <= 'z'))
			
		if(!(s1[i] >= 'a' && s1[i] <= 'z')&&flag !=0 && s1[i - 1] >= 'a' && s1[i - 1] <= 'z'){
			en = i - 1;
			flag = 0;
		//	s2 += s1[i];
		}
		if(s1[i - 1] >= 'a' && s1[i - 1] <= 'z'){
		string w = s1.substr(first, en - first+1);
		//	cout << w << endl;
		//	cout << first << endl;
		bool flag1 = 0;
		for(int j = 0; j < n; j++){
			if((w == a[j])&&(en!=0)){
				//	s2 = s.replace(first, en - first + 1, b[j]);
				//	s = "";
				//	s += s1;
				s2 += b[j];
				//	cout<<first<<en<<endl;
				///	cout<<s<<endl;
					flag1 = 1;
					break;
				}
			}	
			if((flag1 == 0)&&(en!=0)){
				s2 += "UNK";
			//  cout<<first<<en<<endl;
	     	}
	}
	 if(!(s1[i] >= 'a' && s1[i] <= 'z')){
	    	s2 += s1[i];
		}
	}
 //   cout << first << " " << en << " " << endl;
	string w = s1.substr(first, en - first+1);
	bool flag1 = 0;
		for(int j = 0; j < n; j++){
			if((w == a[j])&&(en!=0)){
				//	s2 = s.replace(first, en - first + 1, b[j]);
				//	s = "";
				//	s += s1;
				s2 += b[j];
				//	cout<<first<<en<<endl;
				///	cout<<s<<endl;
					flag1 = 1;
					break;
				}
			}	
			if((flag1 == 0)&&(en!=0)){
				s2 += "UNK";
			//  cout<<first<<en<<endl;
	     	}
	cout << s2;
	return 0; 
}