2.자연수의합

#include <iostream>
using namespace std;

int main() {
    int a, b, i, sum =0;
    cin>>a>>b;
    for(i=a; i<b; i++){
        cout << i<<" + ";
        sum = sum +i;
    }
    cout<<i<<" = ";
    cout<<sum+i;
    
    return 0;
}