package main

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

const (
	mod = int64(1e9 + 7)
)

func resolve(N int, C, D []int64) int64 {
	ret := int64(0)
	for i := 0; i < N; i++ {
		c := C[i] / 2
		if C[i]%2 == 1 {
			c += 1
		}
		ret = (ret + (c%mod)*(D[i]%mod)) % mod
	}
	return ret
}

func main() {
	s := bufio.NewScanner(os.Stdin)

	s.Scan()
	N, _ := strconv.Atoi(s.Text())
	C := make([]int64, N)
	D := make([]int64, N)
	for i := 0; i < N; i++ {
		s.Scan()
		S := strings.Split(s.Text(), " ")
		C[i], _ = strconv.ParseInt(S[0], 10, 64)
		D[i], _ = strconv.ParseInt(S[1], 10, 64)
	}
	fmt.Println(resolve(N, C, D))
}