foo.cc: In function 'int main()':
foo.cc:9:20: warning: 'n1' is used uninitialized in this function [-Wuninitialized]
  int n1,n2,n3,a1[n1],a2[n2],a3[n3];
                    ^
foo.cc:9:27: warning: 'n2' is used uninitialized in this function [-Wuninitialized]
  int n1,n2,n3,a1[n1],a2[n2],a3[n3];
                           ^
foo.cc:9:34: warning: 'n3' is used uninitialized in this function [-Wuninitialized]
  int n1,n2,n3,a1[n1],a2[n2],a3[n3];
                                  ^

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