I want to convert integers to roman numerals, but I receive an error `incompatible types: int cannot be converted to boolean [in MainClass.java]`. It refers to for statement, but I can not see what is wrong.

```
public String intToRoman(int num) {
    if (num < 0 || num > 3999) 
        return Integer.toString(-1);
    int nums[] = {1,4,5,9,10,40,50,90,100,400,500,900,1000}; 
    String[] syms = {"I","IV","V","IX","X","XL","L","XC","C","CD","D","CM","M"}; 
    StringBuilder sb = new StringBuilder();
    int n=0;

    for(int i = 12; 0 ; i--) {

        int res=0;

        if(num > nums[i]) {

            res = num / nums[i];

            for(int j=1 ; res ; j++) {
                sb.append(syms[i]);
            }
        }
    }
    return sb.toString();
}

```