write a go solution for Description:
There are n cities numbered from 1 to n, and city i has beauty a_i.

A salesman wants to start at city 1, visit every city exactly once, and return to city 1.

For all inej, a flight from city i to city j costs max(c_i,a_j-a_i) dollars, where c_i is the price floor enforced by city i. Note that there is no absolute value. Find the minimum total cost for the salesman to complete his trip.

Input Format:
The first line contains a single integer n (2<=n<=10^5) — the number of cities.

The i-th of the next n lines contains two integers a_i, c_i (0<=a_i,c_i<=10^9) — the beauty and price floor of the i-th city.

Output Format:
Output a single integer — the minimum total cost.

Note:
In the first test case, we can travel in order 1to3to2to1.

- The flight 1to3 costs max(c_1,a_3-a_1)=max(9,4-1)=9.
- The flight 3to2 costs max(c_3,a_2-a_3)=max(1,2-4)=1.
- The flight 2to1 costs max(c_2,a_1-a_2)=max(1,1-2)=1.

The total cost is 11, and we cannot do better.. Output only the code with no comments, explanation, or additional text.