unija.cpp: In function 'int main()':
unija.cpp:23:22: error: request for member 'size' in 'v[a.std::map<int, int>::operator[]((y + 1))]', which is of non-class type 'int'
if(v[a[y+1]].size()==0)
^~~~
unija.cpp:29:23: error: request for member 'begin' in 'v[a.std::map<int, int>::operator[]((y + 1))]', which is of non-class type 'int'
if(*v[a[y+1]].begin()<x)
^~~~~
unija.cpp:31:41: error: request for member 'begin' in 'v[a.std::map<int, int>::operator[]((y + 1))]', which is of non-class type 'int'
ms.erase(ms.find(*v[a[y+1]].begin()));
^~~~~
unija.cpp:33:22: error: expected ';' before ']' token
v[a[y+1]]]x;
^