I write this code, but it doesn`t work and i don`t understand why

Code:
#include<stdio.h>
int main(void) {
int decimal[] = { 1000,900,500,400,100,90,50,40,10,9,5,4,1 }; //base values
char symbol[] = { 'M','CM','D','CD','C','XC','L','XL','X','IX','V','IV','I' }; //roman symbols
int i = 0, num;
printf("Enter a number: \n");
scanf_s("%d", &num);
printf("The Roman numeral is: \n");
while (num != 0) { //repeat process until num is not 0
if (num / decimal[i]) { //first base value that divides num is largest base value
printf("%s", symbol[i]); //print roman symbol equivalent to largest base value
num -= decimal[i]; //subtract largest base value from num
}
i++; //move to next base value to divide num
}
return 0;
}