foo.cc: In function 'int main()':
foo.cc:19:4: error: 'ans' was not declared in this scope
    ans.r=max(ansr,a[i].r);
    ^~~
foo.cc:19:4: note: suggested alternative: 'ansr'
    ans.r=max(ansr,a[i].r);
    ^~~
    ansr

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