{"raw_statement":[{"iden":"problem statement","content":"You have $N$ apples, called Apple $1$, Apple $2$, Apple $3$, ..., Apple $N$. The _flavor_ of Apple $i$ is $L+i-1$, which can be negative.\nYou can make an apple pie using one or more of the apples. The flavor of the apple pie will be the sum of the flavors of the apples used.\nYou planned to make an apple pie using all of the apples, but being hungry tempts you to eat one of them, which can no longer be used to make the apple pie.\nYou want to make an apple pie that is as similar as possible to the one that you planned to make. Thus, you will choose the apple to eat so that the flavor of the apple pie made of the remaining $N-1$ apples will have the smallest possible absolute difference from the flavor of the apple pie made of all the $N$ apples.\nFind the flavor of the apple pie made of the remaining $N-1$ apples when you choose the apple to eat as above.\nWe can prove that this value is uniquely determined."},{"iden":"constraints","content":"*   $2 \\leq N \\leq 200$\n*   $-100 \\leq L \\leq 100$\n*   All values in input are integers."},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$N$ $L$"},{"iden":"sample input 1","content":"5 2"},{"iden":"sample output 1","content":"18\n\nThe flavors of Apple $1$, $2$, $3$, $4$, and $5$ are $2$, $3$, $4$, $5$, and $6$, respectively. The optimal choice is to eat Apple $1$, so the answer is $3+4+5+6=18$."},{"iden":"sample input 2","content":"3 -1"},{"iden":"sample output 2","content":"0\n\nThe flavors of Apple $1$, $2$, and $3$ are $-1$, $0$, and $1$, respectively. The optimal choice is to eat Apple $2$, so the answer is $(-1)+1=0$."},{"iden":"sample input 3","content":"30 -50"},{"iden":"sample output 3","content":"\\-1044"}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}