pat1077

#include<cstdio>#include<stack>using namespace std;int main(){//freopen("C:\\Users\\Frank Wang\\Desktop\\in.txt","r",stdin);stack<char> s1,s2,s3;int n;scanf("%d",&n);getchar();char c;while((c=getchar())!='\n'){s1.push(c);}for(int i=1;i<n;i++){while((c=getchar())!='\n'){s2.push(c);}while(!s1.empty()&&!s2.empty()&&s1.top()==s2.top()){s3.push(s1.top());s1.pop();s2.pop();}while(!s1.empty()) s1.pop();while(!s3.empty()){s1.push(s3.top());s3.pop();}while(!s2.empty()) s2.pop();}if(s1.empty()){printf("nai\n");}else{while(!s1.empty()){s2.push(s1.top());s1.pop();}if(s2.top()==' ') s2.pop();while(!s2.empty()){printf("%c",s2.top());s2.pop();}putchar('\n');}}