package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	const M = 1e9+7
	var ans,c,d int64
	for i:=0;i<n;i++ {
		Scan(&c,&d)
		c=(c+1)/2%M
		d%=M
		ans=(ans+c*d%M)%M
	}
	Println(ans)
}