package main

import (
	"bufio"
	"os"
	"strings"
)

type FastScanner struct {
	r *bufio.Reader
}

func NewFastScanner() *FastScanner {
	return &FastScanner{r: bufio.NewReaderSize(os.Stdin, 1<<20)}
}

func (fs *FastScanner) NextInt64() int64 {
	var sign int64 = 1
	var val int64
	c, err := fs.r.ReadByte()
	for (c < '0' || c > '9') && c != '-' {
		c, err = fs.r.ReadByte()
		if err != nil {
			return 0
		}
	}
	if c == '-' {
		sign = -1
		c, _ = fs.r.ReadByte()
	}
	for c >= '0' && c <= '9' {
		val = val*10 + int64(c-'0')
		c, err = fs.r.ReadByte()
		if err != nil {
			break
		}
	}
	if err == nil {
		_ = fs.r.UnreadByte()
	}
	return val * sign
}

func main() {
	fs := NewFastScanner()
	t := int(fs.NextInt64())
	var out strings.Builder

	for ; t > 0; t-- {
		n := int(fs.NextInt64())
		l := make([]int64, n)
		r := make([]int64, n)
		for i := 0; i < n; i++ {
			l[i] = fs.NextInt64()
			r[i] = fs.NextInt64()
		}

		check := func(k int64) bool {
			lo, hi := int64(0), int64(0)
			for i := 0; i < n; i++ {
				if lo-k > l[i] {
					lo = lo - k
				} else {
					lo = l[i]
				}
				if hi+k < r[i] {
					hi = hi + k
				} else {
					hi = r[i]
				}
				if lo > hi {
					return false
				}
			}
			return true
		}

		var left int64 = -1
		var right int64 = 1000000000
		for right-left > 1 {
			mid := (left + right) / 2
			if check(mid) {
				right = mid
			} else {
				left = mid
			}
		}
		out.WriteString(int64ToString(right))
		out.WriteByte('\n')
	}

	w := bufio.NewWriterSize(os.Stdout, 1<<20)
	w.WriteString(out.String())
	w.Flush()
}

func int64ToString(x int64) string {
	if x == 0 {
		return "0"
	}
	var buf [20]byte
	i := len(buf)
	for x > 0 {
		i--
		buf[i] = byte('0' + x%10)
		x /= 10
	}
	return string(buf[i:])
}