[백준] 1292번 : 쉽게 푸는 문제 - C#

https://www.acmicpc.net/problem/1292

using System;

class Program
{
    static void Main() {
        string[] s=Console.ReadLine().Split(' ');
        int n=int.Parse(s[0]);
        int m=int.Parse(s[1]);
        int num=0;
        int a=0;
        int count=0;
        for(int i=1;;i++){
            count+=i;
            a+=i*i;
            if(n-count-1<=i && n!=1){
                num-=a;
                num-=(n-count-1)*(i+1);
                n=10000;
            }
            if(m-count-1<=i){
                num+=a;
                num+=(m-count)*(i+1);
                break;
            }
        }
        Console.Write(num);
    }
}