foo.cc: In function 'int main()':
foo.cc:6:4: error: expected initializer before 'for'
    for(int i=0;i<n;i++)
    ^~~
foo.cc:6:16: error: 'i' was not declared in this scope
    for(int i=0;i<n;i++)
                ^
foo.cc:6:18: error: 'n' was not declared in this scope
    for(int i=0;i<n;i++)
                  ^
foo.cc:8:10: error: 'a' was not declared in this scope
    cout<<a[i<<endl;]
          ^
foo.cc:8:19: error: expected ']' before ';' token
    cout<<a[i<<endl;]
                   ^
foo.cc:8:20: error: expected primary-expression before ']' token
    cout<<a[i<<endl;]
                    ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。