Logarithmic Paprika

The best-selling vegetable in Byteland is the logarithmic paprika. As its name suggests, every paprika weighs a power of two grams. The lightest paprika weighs $2^0 = 1$ gram, and the heaviest weighs $2^k$ grams.

The residents of Byteland dislike buying pieces of a paprika, so sellers must sell only whole paprika. On top of that, the locals are very particular: they will not tolerate a seller who cannot hand over exactly the weight they want to buy. This causes a great deal of stress among the sellers.

A friend of yours who runs a vegetable garden has asked you to write a program to help the sellers. Write a program that:

• reads the current paprika stock from standard input,
• determines the smallest weight that cannot be assembled without cutting any paprika,
• writes the result to standard output.

The first line contains one integer $k$ ($1 \le k \le 10$): the available paprika weights are $2^0, 2^1, \dots, 2^k$ grams. The second line contains $k + 1$ integers $p_0, p_1, \dots, p_k$ ($0 \le p_i \le 1000$), separated by single spaces, describing the current stock: there are $p_0$ paprika of weight $2^0 = 1$ gram, $p_1$ of weight $2^1 = 2$ grams, $\dots$, and $p_k$ of weight $2^k$ grams.

Print a single positive integer $x$: the smallest weight that cannot be assembled without cutting any paprika.

For example, suppose the stock holds two paprika of weight $1$ gram, one of weight $2$ grams, and one of weight $4$ grams. Then every weight from $1$ to $8$ can be assembled: $1 = 1$, $2 = 1 + 1$, $3 = 1 + 2$, $4 = 4$, $5 = 1 + 4$, $6 = 1 + 1 + 4$, $7 = 1 + 2 + 4$, $8 = 1 + 1 + 2 + 4$. The value $9$ cannot be assembled, so the answer for this case is $9$.