【错的次数】

/*
N*logn复杂求出Rank数组以及Sa数组
Rank数组下标是从0开始的,表示的是从i开始的后缀的排名(排名>=1).
Sa数组又是从1开始的,表示的是第i名的(i>=1)后缀是从字符串中的第几个字符开始的(字符位置>=0).
Height[i]从1开始,表示的是字典序为i和字典序为i-1的后缀的最长公共前缀。
*/
#include<bits/stdc++.h>
using namespace std;

const int N = 8e5 + 6000;
const int SN = 2e2;
const int MAX_CHAR = 4500;//每个数字的最大值。
int s[N + 10];//如果是数字,就写成int s[N+10]就好,从0开始存
int Sa[N + 10], T1[N + 10], T2[N + 10], C[N + 10], T;
int Height[N + 10], Rank[N + 10], idx[N + 10], in[N + 10], tag;
char str[SN + 10];

void build_Sa(int n, int m) {
	int i, *x = T1, *y = T2;
	for (i = 0; i<m; i++) C[i] = 0;
	for (i = 0; i<n; i++) C[x[i] = s[i]]++;
	for (i = 1; i<m; i++) C[i] += C[i - 1];
	for (i = n - 1; i >= 0; i--) Sa[--C[x[i]]] = i;
	for (int k = 1; k <= n; k <<= 1)
	{
		int p = 0;
		for (i = n - k; i<n; i++) y[p++] = i;
		for (i = 0; i<n; i++) if (Sa[i] >= k) y[p++] = Sa[i] - k;
		for (i = 0; i<m; i++) C[i] = 0;
		for (i = 0; i<n; i++) C[x[y[i]]]++;
		for (i = 1; i<m; i++) C[i] += C[i - 1];
		for (i = n - 1; i >= 0; i--) Sa[--C[x[y[i]]]] = y[i];
		swap(x, y);
		p = 1; x[Sa[0]] = 0;
		for (i = 1; i<n; i++)
			x[Sa[i]] = y[Sa[i - 1]] == y[Sa[i]] && y[Sa[i - 1] + k] == y[Sa[i] + k] ? p - 1 : p++;
		if (p >= n) break;
		m = p;
	}
}

void getHeight(int n)
{
	int i, j, k = 0;
	for (i = 1; i <= n; i++) Rank[Sa[i]] = i;
	for (i = 0; i<n; i++) {
		if (k) k--;
		j = Sa[Rank[i] - 1];
		while (s[i + k] == s[j + k]) k++;
		Height[Rank[i]] = k;
	}
}

void check(int pos, int i, int &num) {
	if (in[idx[Sa[pos]]] != i) {
		num++;
		in[idx[Sa[pos]]] = i;
	}
}

bool ok(int len, int n) {
	for (int i = 1; i <= T; i++) in[i] = 0;
	for (int i = 2; i <= n; i++)
		if (Height[i] >= len) {
			int j = i, num = 1;
			in[idx[Sa[i - 1]]] = i;
			check(i, i, num);
			while (j + 1 <= n && Height[j + 1] >= len) {
				j++;
				check(j, i, num);
			}
			if (num == T) {
				tag = Sa[i - 1];
				return true;
			}
			i = j;
		}
	return false;
}

int main() {
	//freopen("F:\\rush.txt", "r", stdin);
	ios::sync_with_stdio(0), cin.tie(0);
	while (cin >> T && T) {
		int n = 0;
		for (int i = 1; i <= T; i++) {
			cin >> str;
			for (int j = 0; j < (int)strlen(str); j++) {
				idx[n] = i;
				s[n++] = str[j];
			}
			s[n++] = 300 + i;
		}
		s[n] = 0;
		build_Sa(n + 1, MAX_CHAR);//注意调用n+1
		getHeight(n);
		int l = 1, r = 200, temp = 0;
		while (l <= r) {
			int m = (l + r) >> 1;
			if (ok(m, n)) {
				temp = m;
				l = m + 1;
			}
			else
				r = m - 1;
		}
		if (temp == 0) {
			cout << "IDENTITY LOST" << endl;
		}
		else {
			for (int i = tag; i <= tag + temp - 1; i++)
				cout << char(s[i]);
			cout << endl;
		}
	}
	return 0;
}