#include <stdio.h>
int main() {
    int sin_array[9] = {0, 0, 0, 6, 2, 0, 7, 1, 6}; 
	
    if (sin_array[0] == 0){
        return 1;
    }

    // make the result array
    int result[9];
    
    for (int i = 0; i < 9; i++){

        if (i % 2 == 0){
            result[i] = sin_array[i];
        } 

        else {
            
            int product = sin_array[i] * 2; 

            // sum the digits if it is a two-digit number
            if (product > 9){
                
                result[i] = 1 + (product % 10);
            } 

            else {
                
                result[i] = product;
            }
        }
    }

    // sum the result

    int sum = 0;

    for (int i = 0; i < 9; i++){
        sum += result[i];
    }

    if (sum % 10 != 0){
        return 1;
    }

    return 0;

}

the code above checks if a social insurance number is valid. it does this by first checking if the first digit is 0. if it is, the function returns 1, indicating that the SIN is invalid. if the first digit is not 0, the function proceeds to multiply every other digit by 2 and sum the digits of the resulting number if it is a two-digit number. the function then sums the result array and checks if the sum is divisible by 10. if it is, the function returns 0, indicating that the SIN is valid. if it is not, the function returns 1, indicating that the SIN is invalid.