开灯 - 洛谷

"""

P1161 开灯（python3实现）
https://www.luogu.com.cn/problem/P1161

"""

a=[0]*2000001

n=int(input())

for i in range(1,n+1):

            x,y=map( float,input().split() )

            for j in range(1,int(y+1) ):

                        if a[int(j*x)]==0:
                                    a[int(j*x)]=1

                        else:
                                    a[int(j*x)]=0


i=1

while 1:
            if a[i]==1:
                        print(i)
                        break
            i+=1