View Compilation Error

389529_0_0_10792.cpp: In function `std::string f1(int)':
389529_0_0_10792.cpp:9: error: invalid conversion from `int' to `const char*'
389529_0_0_10792.cpp:9: error:   initializing argument 2 of `std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, _Traits, _Alloc>::insert(typename _Alloc::size_type, const _CharT*) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]'