#include<iostream>
using namespace std;
int sum(int a, int b)
{
 int sum=0;

 if(a<0||b<0)
  throw "음수처리안됨";


 else if(a>b)
  throw "잘못된 입력";


 else for(int i=a;i<=b;i++)
  sum=i+sum;
 
 return sum;
};



int main() {
 try {
  cout << sum(1,3)<<endl;
  cout << sum(2,5) << endl;
  cout << sum(-1,5) << endl;
  cout << sum(5,2)<<endl;
  
 }
 catch(char* s) {
  cout << s << endl;
 }
}



sum함수  어떻게짜는겨