int main (void)
{
int d, i1, i2, i3, i4, i5, i6, i7, i8, i9, i10;
int fir_sum, sec_sum, total;
printf("Enter the first (single) digit: ");
scanf("%1d", &d);
printf("Enter the first group of five digits: ");
scanf("%1d%1d%1d%1d%1d", &i1, &i2, &i3, &i4, &i5);
printf("Enter the second group of five digits: ");
scanf("%1d%1d%1d%1d%1d", &i6, &i7, &i8, &i9, &i10);
fir_sum = d + i2 + i4 + i6 + i8 + i10;
sec_sum = i1 + i3 + i5 +i7 + i9;
total = 3 * fir_sum + sec_sum;
printf("Check digit: %d\n", 9 - (total - 1) % 10);
return 0;
}