The last two digits of the product multiplied by 199 1 1990 is 0, so we only need to consider the last two digits of the product multiplied by 1990 1. The last two digits of 1 199 1 are the product of 9 1, 2 199 1, and 3199/kloc-. The last two digits of11199 1 are 91,so we can see that 10 cycles, that is, the period is 10,190/.

00+0 1=0 1

The answer is 0 1.

The answer is found in Baidu Library. There are several periodic questions with detailed explanations.