foo.cc:9:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
foo.cc: In function 'int main()':
foo.cc:28:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<a.size();j++)
               ~^~~~~~~~~
foo.cc:38:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(int i=t;i<=m;i+=t)cout<<leng[i]<<' ';cout<<endl;
  ^~~
foo.cc:38:43: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
  for(int i=t;i<=m;i+=t)cout<<leng[i]<<' ';cout<<endl;
                                           ^~~~
foo.cc:39:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(int i=m+n-1;i>=t-1;i-=t)cout<<a[i]<<' ';cout<<endl;
  ^~~
foo.cc:39:46: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
  for(int i=m+n-1;i>=t-1;i-=t)cout<<a[i]<<' ';cout<<endl;
                                              ^~~~

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