View Compilation Error

0_0_39824064_13525.c:2:1: error: unknown type name 'using'
    2 | using namespace std;
      | ^~~~~
0_0_39824064_13525.c:2:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
    2 | using namespace std;
      |                 ^~~
0_0_39824064_13525.c:5:15: error: variably modified 'a' at file scope
    5 | ll n, k, cnt, a[maxn], b[maxn];
      |               ^
0_0_39824064_13525.c:5:24: error: variably modified 'b' at file scope
    5 | ll n, k, cnt, a[maxn], b[maxn];
      |                        ^