template <typename Iterator> float F(Iterator begin, Iterator end)
{     
 Iterator i;
 node *medis;
 node * medis = new node ;
 if ((i = find(begin,end,'+')) != end) {
 medis.operation = *i;
 medis->kaire = F(begin,i); medis->desne = F(i+1,end) ;
 return medis;
 }else if ((i = find(begin,end,'-')) != end) {
 medis.operation = *i;
 medis->kaire = F(begin,i); medis->desne = F(i+1,end) ;
 return medis;
 }else if ((i = find(begin,end,'*')) != end) {
 medis.operation = *i;
 medis->kaire = F(begin,i); medis->desne = F(i+1,end) ;
 return medis;
 }else if ((i = find(begin,end,'/')) != end) {
 medis.operation = *i;
 medis->kaire = F(begin,i); medis->desne = F(i+1,end) ;
 return medis;
 }else if ((i = find(begin,end,'^')) != end) {
 medis.operation = *i;
 medis->kaire = F(begin,i); medis->desne = F(i+1,end) ;
 return medis;  
 }else { string str1(begin,end) ;
               istringstream stream(str1);
               float i;
               stream >> i;
               medis.value = i;
 	       return medis;              
      }
}