Main.cc:2:17: error: ‘srd’ is not a namespace-name using namespace srd; ^~~ Main.cc:2:20: error: expected namespace-name before ‘;’ token using namespace srd; ^ Main.cc: In function ‘int main()’: Main.cc:6:2: error: ‘cin’ was not declared in this scope cin>>n>>m; ^~~ Main.cc:6:2: note: suggested alternative: In file included from Main.cc:1:0: /usr/include/c++/7/iostream:60:18: note: ‘std::cin’ extern istream cin; /// Linked to standard input ^~~ Main.cc:15:4: error: ‘cout’ was not declared in this scope cout<& __os) ^~~~