from math import ceil
import sys
def main():
    input = sys.stdin.readline
    MOD = 10**9 + 7
    N = int(input())
    t = 0
    for _ in range(N):
        c,d = map(int, input().split())
        t = (t + ceil(c/2) * d)%MOD
    print(t)

if __name__ == "__main__":
    main()