After transformation, it becomes cdab.

By increasing this value by 5940, we can draw several conclusions:

1. It is obtained by adding 0 to a single digit: b = d.

2. When the number of10 digits is increased from 100 digits to 9 digits, it must be carried.

There are ten numbers with a difference of 4, but there is a carry: a+ 10-c=4.

That is, c-a=6.

C is 7.8.9.

A is1.2.3 (a >); 0)

Because it is the smallest, A = 1, C = 7.

Next, determine B and D. Of course, 0 is the best, but the condition of the topic divided by 9 is greater than 8, which is an odd number.

So we analyze it again.

First of all, the current result is 1b7d, so 1b7d+ 1 can be divisible by 9.

The condition of being divisible by 9 is that the sum of each number can be divisible by 9.

That is, 1+b+7+d+ 1 is divisible by 9.

Because b=d, 9+b+d can be divisible by 9.

Because it's weird

When b=d=9, it is the smallest odd number.

Inspection:1979/9 = 219 ...

79 19- 1979=5940

So this number is 1979.