#include <iostream>
using namespace std;

#define smth

int main() {

    #ifdef smth
        puts("smth is defined");
    #elseif 
        puts("smth is not defined");
    #endif

    #ifndef smth // #ifnfed = !ifdef
        puts("smth is not defined");
    #elseif 
        puts("smth is defined");
    #endif
    return 0;
}