foo.cc: In function 'int main()':
foo.cc:8:16: warning: 'n1' is used uninitialized in this function [-Wuninitialized]
  int n1,n2,a[n1],b[n2];
                ^
foo.cc:8:22: warning: 'n2' is used uninitialized in this function [-Wuninitialized]
  int n1,n2,a[n1],b[n2];
                      ^

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