Problem Statement

Mitsubachi went bowling on the day of his graduation ceremony to commemorate it.
This bowling game has $N$ turns, and in the $i$-th turn, $p_i$ pins are set up.
In this bowling game, a ball is thrown exactly once in each turn, and a score equal to the number of pins knocked down is given.
Then, if exactly $a_i$ pins are knocked down, the number of pins knocked down in the next turn is added to the score of the $i$-th turn (unless it is the $N$-th turn). The final score is the sum of the scores of all turns.
In fact, Mitsubachi is a professional bowler, so he can knock down any number of pins he likes. What is the maximum final score Mitsubachi can obtain?

Input

$N$
$p_1 \ \ a_1$
$p_2 \ \ a_2$
$\ \vdots$
$p_n \ \ a_n$

All inputs are integers.
$1 \leq N \leq 10^5$
$1 \leq p_i \leq 10^4$
$1 \leq a_i \leq p_i$

Output

Output the answer on $1$ line.
Print a newline at the end.

Sample

2
3 2
4 2

10

2
1 1
1 1

3

Source

Nada High School 75th Class Junior High Graduation Commemorative Contest: Strange Bowling
writer: karudano
tester: Mitarushi
Ported in accordance with the HackerRank terms of service. Some parts have been modified.