Main.cc: In function ‘int main()’: Main.cc:14:20: warning: init-statement in selection statements only available with -std=c++1z or -std=gnu++1z if(j%m==0;){ ^ Main.cc:14:23: warning: statement has no effect [-Wunused-value] if(j%m==0;){ ~~~^~~ Main.cc:14:27: error: expected primary-expression before ‘)’ token if(j%m==0;){ ^