Problem:
Score : 200 points

Problem Statement

A group of people played a game. All players had distinct scores, which are positive integers.

Takahashi knows N facts on the players' scores. The i-th fact is as follows: the A_i-th highest score among the players is B_i.

Find the maximum possible number of players in the game.

Constraints

1 \leq N \leq 10^5

1 \leq A_i \leq 10^9(1\leq i\leq N)

0 \leq B_i \leq 10^9(1\leq i\leq N)

If i ≠ j, A_i ≠ A_j.

There exists a possible outcome of the game that are consistent with the facts.

All input values are integers.

Inputs

Input is given from Standard Input in the following format:

N
A_1 B_1
:
A_N B_N

Outputs

Print the maximum possible number of players in the game.

Sample Input 1

3
4 7
2 9
6 2

Sample Output 1

8

The maximum possible number of players is achieved when, for example, the players have the following scores: 12,9,8,7,5,2,1,0.

Sample Input 2

5
1 10
3 6
5 2
4 4
2 8

Sample Output 2

7

Sample Input 3

2
1 1000000000
1000000000 1

Sample Output 3

1000000001

Solution in Go (1.6) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var (
	N      int
	answer = 1234567890123456
)

func readVariables() {
	N = nextInt()
}

func main() {
	readVariables()
	for i := 0; i < N; i++ {
		s := nextInt() + nextInt()
		answer = MinInt(s, answer)
	}
	fmt.Println(answer)
}

/* Template */

var scanner *bufio.Scanner

func init() {
	Max := 1001001
	scanner = bufio.NewScanner(os.Stdin)
	scanner.Buffer(make([]byte, 0, Max), Max)
	scanner.Split(bufio.ScanWords)
}

//nextInt converts next token from stdin and returns integer value.
//nextInt panics when conversion into an integer fails.
func nextInt() int {
	if !scanner.Scan() {
		panic("No more token.")
	}
	num, err := strconv.Atoi(scanner.Text())
	if err != nil {
		panic("nextInt(): cannot convert to int: " + scanner.Text())
	}
	return num
}

func nextStr() string {
	if !scanner.Scan() {
		panic("No more token.")
	}
	return scanner.Text()
}

// MinInt returns minimum argument
func MinInt(x, y int) int {
	if x < y {
		return x
	} else {
		return y
	}
}

//MaxInt returns maximum argument
func MaxInt(x, y int) int {
	if x < y {
		return y
	} else {
		return x
	}
}

//AbsInt returns |x| for x
func AbsInt(x int) int {
	if x < 0 {
		return -x
	}
	return x
}

//ModPow calculates integer power with modulo operation
//if modulo <= 1, it powers w/o module operation
//if base < 0, return value might be negative too.
func ModPow(base, exponent, modulo int) (result int) {
	result = 1
	for exponent > 0 {
		if exponent%2 == 1 {
			result *= base
			if modulo > 1 {
				result %= modulo
			}
		}
		base *= base
		if modulo > 1 {
			base %= modulo
		}
		exponent /= 2
	}
	return
}

//Gcd
func Gcd(vals ...int) (result int) {
	if len(vals) == 0 {
		return
	}
	result = vals[0]
	for i := 1; i < len(vals); i++ {
		result = gcd(result, vals[i])
	}
	return
}

func gcd(x, y int) int {
	x, y = AbsInt(x), AbsInt(y)
	for y > 0 {
		x, y = y, x%y
	}
	return x
}

//Lcm
func Lcm(vals ...int) (result int) {
	if len(vals) == 0 {
		return
	}
	result = vals[0]
	for i := 1; i < len(vals); i++ {
		result = lcm(result, vals[i])
	}
	return
}

func lcm(x, y int) int {
	return x * y / gcd(x, y)
}