Codeforces 455A Boredom - Base Cases

$3.$ Set the base cases

You need to define $dp[0]$ and $dp[1]$. There are no positive numbers when you only consider values up to $0$, so $dp[0] = 0.$ When you consider values up to $1$, the only possible value is $1$. **

You can either take it or not take it. The best is to take all ones, so $dp[1] = 1 \cdot \text{cnt}[1].$ Now, think about the final answer! Take time to work through examples.