/in/foo.cc: In function 'int main()':
/in/foo.cc:29:17: error: no match for 'operator&&' (operand types are 'bool' and 'std::set<int>::iterator {aka std::_Rb_tree_const_iterator<int>}')
    if(vis[i]==0 && s.find(a[i]))vis[i]=1;
       ~~~~~~~~~~^~~~~~~~~~~~~~~
/in/foo.cc:29:17: note: candidate: operator&&(bool, bool) <built-in>
/in/foo.cc:29:17: note:   no known conversion for argument 2 from 'std::set<int>::iterator {aka std::_Rb_tree_const_iterator<int>}' to 'bool'