/in/foo.c: In function 'Unique':
/in/foo.c:7:9: error: unknown type name 'bool'
         bool found_duplicate = false;
         ^~~~
/in/foo.c:7:32: error: 'false' undeclared (first use in this function)
         bool found_duplicate = false;
                                ^~~~~
/in/foo.c:7:32: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:8:130: error: 'true' undeclared (first use in this function)
         for (int k = 0; k <= i && !found_duplicate; ++k) {             if (arr[k] == arr[j]) {                 found_duplicate = true;                 break;             }         }
                                                                                                                                  ^~~~
/in/foo.c: In function 'main':
/in/foo.c:16:47: error: 'n1' undeclared (first use in this function)
     int a1[101], a2[101];     scanf("%d %d", &n1, &n2);
                                               ^~
/in/foo.c:16:52: error: 'n2' undeclared (first use in this function)
     int a1[101], a2[101];     scanf("%d %d", &n1, &n2);
                                                    ^~