/in/foo.c:2:1: error: unknown type name 'using'
    2 | using namespace std;
      | ^~~~~
/in/foo.c:2:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
    2 | using namespace std;
      |                 ^~~
/in/foo.c: In function 'main':
/in/foo.c:9:3: error: unknown type name 'bool'
    9 |   bool flag = 1;
      |   ^~~~
/in/foo.c:10:13: error: 'new' undeclared (first use in this function)
   10 |   int* p1 = new int[n] {};
      |             ^~~
/in/foo.c:10:13: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:10:17: error: expected ',' or ';' before 'int'
   10 |   int* p1 = new int[n] {};
      |                 ^~~
/in/foo.c:11:17: error: expected ',' or ';' before 'int'
   11 |   int* p2 = new int[n-1] {};
      |                 ^~~
/in/foo.c:16:16: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
   16 |    p2[i - 1] = abs(p1[i] - p1[i - 1]);
      |                ^~~
/in/foo.c:36:3: error: 'delete' undeclared (first use in this function)
   36 |   delete[]p1; p1 = NULL;
      |   ^~~~~~
/in/foo.c:36:10: error: expected expression before ']' token
   36 |   delete[]p1; p1 = NULL;
      |          ^
/in/foo.c:37:10: error: expected expression before ']' token
   37 |   delete[]p2; p2 = NULL;
      |          ^
/in/foo.c:12:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   12 |   scanf("%d", &p1[0]);
      |   ^~~~~~~~~~~~~~~~~~~
/in/foo.c:15:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   15 |    scanf("%d", &p1[i]);
      |    ^~~~~~~~~~~~~~~~~~~