/in/foo.cc: In function 'int main()':
/in/foo.cc:60:16: error: 'na' was not declared in this scope
  nc=InterSet(a,na,  b,nb,  c);
                ^~
/in/foo.cc:60:23: error: 'nb' was not declared in this scope
  nc=InterSet(a,na,  b,nb,  c);
                       ^~
/in/foo.cc:61:23: error: 'nm' was not declared in this scope
  nc=InterSet(a,na,  m,nm,  c);
                       ^~
/in/foo.cc:54:6: warning: unused variable 'i' [-Wunused-variable]
  int i,n1,n2 ,n3; cin>>n1>>n2>>n3;
      ^