#include <iostream>#include <cstdlib>#include <vector>#include <string>using namespace std;int main() {    int n = 0;    cin>>n;    getchar();    vector<string> strs;    for (int i=0; i<n; i++) {        string line;        getline(cin, line, ‘\n‘);        strs.push_back(line);    }        int i;    for (i=0; i<256; i++) {        char ch = ‘\0‘;        int j;        for (j=0; j<n; j++) {            int len = strs[j].size();            if (i >= len) break;            if (j == 0) {                ch = strs[j][len - i - 1];                continue;            }            if (ch != strs[j][len - i - 1]) break;        }        if (j != n) break;    }    if (i == 0) {        cout<<"nai"<<endl;    } else {        cout<<strs[0].substr(strs[0].size() - i)<<endl;    }    return 0;}