阿拉伯数字转化成罗马字符

#include<iostream>
#include<vector>
#include<string>
using namespace std;
int main()
{
    int num;
    cin>>num;
    string result;
    int a1[]={1000,900,500,400,100,90,50,40,10,9,5,4,1};
    string a2[]={"M", "CM", "D", "CD", "C", "XC","L", "XL", "X", "IX", "V", "IV", "I"};
    int i=0;
    while(num>0)
    {
        int count=num/a1[i];
        while(count--)
            result+=a2[i];
        num=num%a1[i];
        i++;
    }
    cout<<result<<endl;
}