# -*- coding:utf-8 -*-
if __name__ == '__main__':
    mod = (10 ** 9) + 7

    n = int(input())
    cnt = 0
    for i in range(n):
        c, d = map(int, input().split())
        c = (c + 1) // 2  % mod
        d %= mod
        cnt += c * d
        cnt %= mod
    print(cnt)