<|system|>
Find the units digit of $7 \cdot 17 \cdot 1977 - 7^3$</s>.
<|user|>
Can you answer based on context?
<|assistant|>
The units digit of a product or difference depends only on the units digits of the factors or terms. So I can ignore everything except the last digits of the numbers involved. The units digit of $7 \cdot 17 \cdot 1977 - 7^3$ is the same as the units digit of $7 \cdot 7 \cdot 7 - 7^3$, since $17$ and $1977$ both end in $7$. This simplifies to $7^3 - 7^3$. Since $7^3$ ends in $3$, the units digit of $7^3 - 7^3$ is $3 - 3$, which is $0$. Therefore, the units digit of the original expression is $0$. 