while (n>0)
      {
            b=a;
            b=b/pow(10,n-1) - rezult/pow(10,n-1);
            for (int i=1;i<10;i++)
            if ((b-i>=0)&(b-i-1<0))  rezult += (i)*pow(10,n-1);
            n--;
      }
/*
if delete :

b=b/pow(10,n-1) - rezult/pow(10,n-1);
            for (int i=1;i<10;i++)
            if ((b-i>=0)&(b-i-1<0))  rezult += (i)*pow(10,n-1);

- work! */

1. Which programming language do you use?
2. Did you name the variable for result "rezult" (if there is need to pre-declare variables in yout PL)?