#include <iostream.h>
#include <stdlib.h>
#include <string.h>

// =========================================================================================

class TStringExpr {
   private:
      string expr;
      unsigned int cur;
   public:
      TStringExpr() { expr=""; cur=0; };
      TStringExpr(char *str) { expr=str; cur=0; };
      TStringExpr(const string &str) { expr=str; cur=0; };
      string operator=(char *str);
      string operator=(const string &str);
      void putback(char ch) { if(cur>0) expr[--cur]=ch; };
      char get() { return cur<expr.length() ? expr[cur++] : 0; };
      void unget() { if(cur>0) cur--; };
      void print_wrong_char(char *fname);
      // ----------------
      friend istream& operator>>(istream &inp, TStringExpr &e);
      friend ostream& operator<<(ostream &out, const TStringExpr &e);
      friend char operator>>(TStringExpr &e, char &ch);
      friend TStringExpr& operator>>(TStringExpr &e, int &value);
};

string TStringExpr::operator=(char *str)
{
   expr = str;
   cur = 0;
   return expr;
}

string TStringExpr::operator=(const string &str)
{
   expr = str;
   cur = 0;
   return expr;
}

void TStringExpr::print_wrong_char(char *fname)
{
   cerr<<expr<<endl;
   for(unsigned int i=0;i<cur-1;i++) cerr<<"";
   cerr<<"^"<<endl;
   cerr<<"Error in function "<<fname<<": wrong character '"<<expr[cur]<<"'"<<endl;
}


istream& operator>>(istream &inp, TStringExpr &e)
{
	char ch;
   e.expr = "";

	ch = inp.get();
	while( !inp.eof() && ch!='\n' ){
      if( ! isspace(ch) )
		   e.expr += ch;
	   ch = inp.get();
	}
   e.cur = 0;
   return inp;
}

ostream& operator<<(ostream &out, const TStringExpr &e)
{
   out<<e.expr;
   return out;
}

char operator>>(TStringExpr &e, char &ch)
{
	if( e.cur < e.expr.length() )
      return ch=e.expr[e.cur++];
	else return 0;
}

TStringExpr& operator>>(TStringExpr &e, int &value)
{
   char ch;
   value = 0;
   while( ch=e.get() )
      if( isdigit(ch) ) value = 10*value + (ch-'0');
      else{ e.unget(); break; }
   return e;
}

// =========================================================================================


/* -------------------------------------
   Grammar:
   epression ::= term
                 term + expression
                 term - expression

   term      ::= factor
                 factor * term
                 factor / term

   factor    ::= number
                 - factor
                 ( expression )
   ------------------------------------- */

int eval_expr(TStringExpr &expr);

int eval_factor(TStringExpr &expr)
{
	int  res;
	char ch;

	if( expr>>ch )
		if( ch=='(' || ch=='-' || isdigit(ch) ){
			if( ch == '(' ){
				res = eval_expr(expr);
				if( !(expr>>ch) || ch != ')' ){
               expr.print_wrong_char("eval_factor()");
					exit(1);
				}
			}
			else if( ch == '-' ){
				res = - eval_factor(expr);
			}
			else{
				expr.unget();
				expr>>res;
			}
		}
		else{
         expr.print_wrong_char("eval_factor()");
			exit(1);
		}
		return res;
}

int eval_term(TStringExpr &expr)
{
	char ch;
	int left, right;

	left = eval_factor(expr);
cerr<<"eval_term(): left = "<<left<<endl;
	while( expr>>ch ){
		if( ch=='*' || ch=='/' ){
			right = eval_factor(expr);
cerr<<"eval_term(): right = "<<right<<endl;
cerr<<"eval_term(): operatiorn: "<<ch<<endl;
			if( ch == '*' ) left *= right;
			else if( right != 0 )  left /= right;
			else{
				cerr<<"Error: Division by zero!\n";
				exit(1);
			}
		}
		else if( ch=='+' || ch=='-' || ch==')' ){ expr.unget(); break; }
		else{
         expr.print_wrong_char("eval_term()");
			exit(1);
		}
   }
	return left;
}

int evaluate(TStringExpr &expr)
{
   char ch;
   int  res = eval_expr(expr);
   if( expr>>ch ){
      expr.print_wrong_char("evaluate()");
		exit(1);
   }
   return res;
}

int eval_expr(TStringExpr &expr)
{
	char ch;
	int  left, right;

	left = eval_term(expr);
cerr<<"eval_expr(): left = "<<left<<endl;
	while( expr>>ch ){
		if( ch=='+' || ch=='-' ){
			right = eval_term(expr);
cerr<<"eval_expr(): right = "<<right<<endl;
cerr<<"eval_expr(): operatiorn: "<<ch<<endl;
			if( ch == '+' ) left += right;
			else left -= right;
		}
		else if( ch==')' ){ expr.unget(); break; }
		else{
         expr.print_wrong_char("eval_expr()");
			exit(1);
		}
   }
	return left;
}

void main()
{
	int  res;
   TStringExpr expr("-2+4*3+5/4-(10-2)");

   cin>>expr;

   cout<<"Evaluating '"<<expr<<"'\n";
	res = evaluate(expr);

	cout<<"res = "<<res<<endl;
}