[R] overlapping intervals

[Giovanni Coppola]

Hello everybody,

I have two series of intervals, and I'd like to output the shared  
regions.
For example:
series1<-cbind(Start=c(10,21,40,300),End=c(20,26,70,350))
series2<-cbind(Start=c(25,60,210,500),End=c(40,100,400,1000))

 > series1
      Start End
[1,]    10  20
[2,]    21  26
[3,]    40  70
[4,]   300 350
 > series2
      Start  End
[1,]    25   40
[2,]    60  100
[3,]   210  400
[4,]   500 1000

I'd like to have something like this as result:
 > shared
      Start End
[1,]    25  26
[2,]    60  70
[3,]   300 350

I found this post, but the solution finds the regions shared across  
all the intervals.
http://finzi.psych.upenn.edu/R/Rhelp02a/archive/59594.html
Can anybody help me with this?
Thanks
Giovanni