/in/foo.c:12:1: error: unknown type name 'bool'
 bool isp[MAXN];
 ^~~~
/in/foo.c:27:1: error: unknown type name 'bool'
 bool IsPrime(ll x)
 ^~~~
/in/foo.c: In function 'IsPrime':
/in/foo.c:29:10: warning: suggest parentheses around arithmetic in operand of '^' [-Wparentheses]
     if(x & 1 ^ 1) return false;
        ~~^~~
/in/foo.c:29:26: error: 'false' undeclared (first use in this function)
     if(x & 1 ^ 1) return false;
                          ^~~~~
/in/foo.c:29:26: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:32:12: error: 'true' undeclared (first use in this function)
     return true;
            ^~~~
/in/foo.c: In function 'dfs':
/in/foo.c:38:15: error: 'std' undeclared (first use in this function)
         ans = std::min(ans, res);
               ^~~
/in/foo.c:38:18: error: expected ';' before ':' token
         ans = std::min(ans, res);
                  ^
/in/foo.c:43:18: error: expected ';' before ':' token
         ans = std::min(ans, res * (rem + 1));
                  ^
/in/foo.c: In function 'IsPrime':
/in/foo.c:33:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^