用条件表达式 输入某月某日，判断这一天是这一年的第几天

用条件表达式
输入某月某日，判断这一天是这一年的第几天

#include <iostream>
using namespace std;
int main()
{
    int year,mon,day;
    int i,sum = 0;
    int arr[]={0,31,28,31,30,31,30,31,31,30,31,30,31};
    cin >> year >> mon >> day;
    if(year%4==0 && year%100 != 0 || year%400 == 0)
        arr[2] = 29;
    for (i=0;i<mon;i++)
    {
        sum += arr[i];
    }
    sum += day;
    cout << year <<"年" << mon << "月共有"<< arr[mon]<<"天" << endl;
    cout <<year <<"年" << mon <<"月" << day<<"日是今年的第" << sum <<"天"<<endl;
    return 0;
}