#146 test
import math
N=int(input())
C=[[float(i) for i  in input(). split ()] for i in range(N)]
S=0
M=10*10
for i in range(7):
    M*=10
M+=7
for i in range(N):
    if C[i][0]/2!=math.floor(C[i][0]/2):
        C[i][0]+=1
    e=C[i][0]/2
    e=e*C[i][1]
    e=e-math.floor(e/M)
    S+=e
S=int(S)
S%=M
print (S)