#include <stdbool.h> #include <stdio.h> #include <string.h> int main() { char s[1001] = {}; char c; int length = 0; int sum = 0; bool flag = false; scanf("%s", s); length = strlen(s); for (int i=0; i<length; ++i) { sum = 0; for (int j=0; j<length; ++j) { if (s[i] == s[j]) sum++; else {} } if (sum == 1) { printf("%c", s[i]); flag = true; break; } else {} } if (!flag) { printf("-1"); } return 0; }