View Compilation Error

0_0_37232564_762.c:3:1: error: unknown type name 'using'
 using namespace std;
 ^
0_0_37232564_762.c:3:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
 using namespace std;
                 ^
0_0_37232564_762.c:4:1: error: expected identifier or '(' before '/' token
 //Lucas https://blog.csdn.net/deaidai/article/details/89061972
 ^
0_0_37232564_762.c:6:8: error: 'maxn' undeclared here (not in a function)
 ll fac[maxn];
        ^
0_0_37232564_762.c: In function 'init':
0_0_37232564_762.c:9:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for(int i = 1; i <= p; i++)
     ^
0_0_37232564_762.c:9:5: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_37232564_762.c: In function 'main':
0_0_37232564_762.c:48:3: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
   for(ll i=k+1;i<=n;i++)
   ^