Main.cc: In function ‘bool big(std::__cxx11::string, std::__cxx11::string)’: Main.cc:25:27: error: invalid use of member function ‘std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size() const [with _CharT = char; _Traits = std::char_traits; _Alloc = std::allocator; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type = long unsigned int]’ (did you forget the ‘()’ ?) rt ( x . size ( ) == y . size ? ( x > y ) : x . size ( ) > y . size ( ) ) ; ~~~~^~~~ Main.cc: In function ‘bool cmp(data, data)’: Main.cc:29:9: error: ‘x’ was not declared in this scope return x . a * x . b > y . a * y . b ; ^ Main.cc:29:25: error: ‘y’ was not declared in this scope return x . a * x . b > y . a * y . b ; ^ Main.cc: In function ‘std::__cxx11::string div(std::__cxx11::string, long long int)’: Main.cc:45:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int i = 0 ; i < a . size ( ) ; i ++ ) ~~^~~~~~~~~~~~~~ Main.cc:47:3: error: ‘ans’ was not declared in this scope ans += ( ( x * 10 + ( a [i] - '0' ) ) / b ) + '0' ; ^~~ Main.cc:47:3: note: suggested alternative: ‘abs’ ans += ( ( x * 10 + ( a [i] - '0' ) ) / b ) + '0' ; ^~~ abs Main.cc:50:10: error: ‘ans’ was not declared in this scope while ( ans [0] == 0 && ans . size ( ) > 0 ) ^~~ Main.cc:50:10: note: suggested alternative: ‘abs’ while ( ans [0] == 0 && ans . size ( ) > 0 ) ^~~ abs Main.cc:54:5: error: ‘ans’ was not declared in this scope rt ans ; ^~~ Main.cc:54:5: note: suggested alternative: ‘abs’ rt ans ; ^~~ abs Main.cc: In function ‘int main()’: Main.cc:66:2: error: ‘atring’ was not declared in this scope atring am = tstr ( man [1] . num ) ^~~~~~ Main.cc:66:2: note: suggested alternative: ‘stdin’ atring am = tstr ( man [1] . num ) ^~~~~~ stdin Main.cc:67:20: error: ‘i’ was not declared in this scope for ( int i = 1 ; i <= n ; i ++ ) ^