/in/foo.c:2:1: error: unknown type name 'LL'
 const LL MOD = 1e9+7;
 ^
/in/foo.c: In function 'pow_mod':
/in/foo.c:10:16: error: 'A' undeclared (first use in this function)
    i = i*a%(LL)A;
                ^
/in/foo.c:10:16: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c: In function 'main':
/in/foo.c:17:20: error: 'n' undeclared (first use in this function)
     scanf("%lld", &n);
                    ^