Internet

Tomas's internet connection is often unstable, and sometimes it drops out entirely. Tomas wants to know how long he might have to wait for a dropped connection to come back, so every now and then he checks whether he has an internet connection at that moment and writes it down.

Tomas remembers that he had a connection during both the first and the last measurement.

Help Tomas find the longest time he could possibly have gone without internet.

The first line contains a single integer $N$, the number of measurements Tomas made.

Each of the next $N$ lines contains two integers $T_i$ and $M_i$. $T_i$ is the time at which Tomas took the $i$-th measurement, and $M_i$ is its result: $M_i$ is $1$ if he had an internet connection at that moment, or $0$ if he did not.

The measurements are given in increasing order of $T_i$.

Print a single integer: the longest time interval during which Tomas could have been without internet.

• $2 \le N \le 1000$
• $1 \le T_i \le 10^6$
• $T_i < T_{i+1}$