Main.cc: In function ‘int main()’: Main.cc:6:5: error: ‘max’ was not declared in this scope max=b; ^~~ Main.cc:6:5: note: suggested alternative: In file included from /usr/include/c++/7/bits/char_traits.h:39:0, from /usr/include/c++/7/ios:40, from /usr/include/c++/7/ostream:38, from /usr/include/c++/7/iostream:39, from Main.cc:1: /usr/include/c++/7/bits/stl_algobase.h:265:5: note: ‘std::max’ max(const _Tp& __a, const _Tp& __b, _Compare __comp) ^~~ Main.cc:5:10: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d",&a,&b,&c); ~~~~~^~~~~~~~~~~~~~~~~~~~~