/in/foo.c:3:1: error: expected ',' or ';' before 'int'
 int a[N] = {10}
 ^~~
/in/foo.c: In function 'main':
/in/foo.c:70:46: error: 'a' undeclared (first use in this function)
     for (int i = 0; i < n; ++i) scanf("%d", &a[i]);
                                              ^
/in/foo.c:70:46: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c: In function 'swap':
/in/foo.c:7:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^