Main.cc: In function 'int main()': Main.cc:11:28: error: 't' was not declared in this scope for(int j=i;j=1&&t<=n*n;j--){ ^ Main.cc:20:23: error: unable to find numeric literal operator 'operator""i' for(int j=n-i-2i;j>1&&t<=n*n;j--){ ^ Main.cc:20:23: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes Main.cc:20:31: error: 't' was not declared in this scope for(int j=n-i-2i;j>1&&t<=n*n;j--){ ^