errors for phone number suggestion

main.cpp: In function ‘int main()’:
main.cpp:18:5: error: ‘input’ was not declared in this scope
     input.ignore(std::numeric_limits<std::streamsize>::max(), '\n'
     ^
main.cpp:18:18: error: ‘numeric_limits’ is not a member of ‘std’
     input.ignore(std::numeric_limits<std::streamsize>::max(), '\n'
                  ^
main.cpp:18:53: error: expected primary-expression before ‘>’ token
     input.ignore(std::numeric_limits<std::streamsize>::max(), '\n'
                                                     ^
main.cpp:18:60: error: no matching function for call to ‘max()’
   input.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
                                                          ^
In file included from /usr/include/c++/5/bits/char_traits.h:39:0,
                 from /usr/include/c++/5/ios:40,
                 from /usr/include/c++/5/ostream:38,
                 from /usr/include/c++/5/iostream:39,
                 from main.cpp:1:
/usr/include/c++/5/bits/stl_algobase.h:219:5: note: candidate: template<class _Tp> const _Tp& std::max(const _Tp&, const _Tp&)
     max(const _Tp& __a, const _Tp& __b)
     ^
/usr/include/c++/5/bits/stl_algobase.h:219:5: note:   template argument deduction/substitution failed:
main.cpp:18:60: note:   candidate expects 2 arguments, 0 provided
   input.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
                                                          ^
In file included from /usr/include/c++/5/bits/char_traits.h:39:0,
                 from /usr/include/c++/5/ios:40,
                 from /usr/include/c++/5/ostream:38,
                 from /usr/include/c++/5/iostream:39,
                 from main.cpp:1:
/usr/include/c++/5/bits/stl_algobase.h:265:5: note: candidate: template<class _Tp, class _Compare> const _Tp& std::max(const _Tp&, const _Tp&, _Compare)
     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
     ^
/usr/include/c++/5/bits/stl_algobase.h:265:5: note:   template argument deduction/substitution failed:
main.cpp:18:60: note:   candidate expects 3 arguments, 0 provided
   input.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
                                                          ^
bash: line 2: ./a.out: No such file or directo