How to plot three lines with different lengths in the same graph

[Durga Gaddam]

Hello Guys I am finding it difficult to plot a graph, Please help me.

I have a data like this

I have created some random data 

set.seed(12155)

weekly_sales <- rnorm(143,mean=22513.32,sd=824.0621)

dates <- (seq(as.Date('2010/02/05'), as.Date('2012/10/26'), by="week"))

week <- 1:143

I need to create a graph like this

With three lines and different lengths in ggplot, Please do not use lubridate function 

Thank you