#include <vector>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;struct SubStr{ const char* str; int id; SubStr(const char *p, int i) : str(p), id(i) { } bool operator<(const SubStr& rhs) const { return strcmp(str, rhs.str) < 0; }};int get_lcs(const char *a, const char *b, char *c){ int l = 0; while (*a != ' ' && *a == *b) { *c = *a; ++l; ++a; ++b; ++c; } *c = ' '; return l;}static char str[4000][256], lcs[256], ans[256];int main(void){ int n, cmp, len; while (scanf("%d", &n) != EOF && n != 0) { vector<SubStr> v; for (int i = 0; i < n; i++) { scanf("%s", str[i]); for (char *p = str[i]; *p != ' '; p++) { v.push_back(SubStr(p, i)); } } sort(v.begin(), v.end()); int cc = 0; vector<int> c(n, 0); vector<SubStr>::const_iterator i = v.begin(), j = v.begin(); strcpy(ans, ""); len = 0; while (true) { while (j != v.end()) { if (c[j->id] == 0) { ++cc; } ++c[j->id]; if (cc == n) { break; } else { ++j; } } if (j == v.end()) { break; } while (c[i->id] > 1) { --c[i->id]; ++i; } cmp = get_lcs(i->str, j->str, lcs); if (cmp > len) { len = cmp; strcpy(ans, lcs); } else if (cmp == len && strcmp(lcs, ans) < 0) { strcmp(ans, lcs); } --cc; --c[i->id]; ++i; ++j; }; if (strcmp(ans, "") == 0) { puts("IDENTITY LOST"); } else { puts(ans); } } return 0;}
