How to I solve this errors please

  1  #include<iostream>
  2  #include<algorithm>
  3  #include<stack>
  4  #include<string>
  5  using namespace std;
  6  
  7  int priority(char c) {
  8  	if (c == '-' || c == '+')
  9  		return 1;
 10  	else if (c == '*' || c == '/')
 11  		return 2;
 12  	else if (c == '^')
 13  		return 3;
 14  	else
 15  		return 0;
 16  
 17  }
 18  
 19  string infixtopostfix(string exp) {
 20  
 21  	stack<char> stk;
 22  	string output = "";
 23  	for (int i = 0; i < exp.length(); i++) {
 24  		if (exp[i] == ' ') { continue; }
 25  		else if (isdigit(exp[i]) || isalpha(exp[i])) {
 26  			output += exp[i];
 27  		}
 28  		else if (exp[i] == '(') {
 29  			stk.push('(');
 30  		}
 31  		else if (exp[i] == ')') {
 32  			while (stk.top() != '(') {
 33  				output += stk.top();
 34  				stk.pop();
 35  			}
 36  
 37  			stk.pop();
 38  		}
 39  		else {
 40  			while (!stk.empty() && priority(exp[i]) <= (priority(stk.top()){
 41  				output += stk.top();
 42  				stk.pop()
 43  			}
 44  			stk.push(exp[i]);
 45  		}
 46  	}
 47  
 48  			while (!stk.empty()) {
 49  				output += stk.top();
 50  				stk.pop();
 51  			}
 52  
 53  			return output;
 54  		
 55  
 56  
 57  
 58  			int main() {			
 59              	string infixexpression = ("(3+2)+7/2*((7+3)*2");
 60  				cout << infixtopostfix(infixexpression) << endl; 
 61  				return 0;
 62  			}