unable-to-access-index-for-repository.R

#install.packages("devtools")
#Warning in install.packages :
#  unable to access index for repository https://cran.rstudio.com/src/contrib:
#  cannot open URL 'https://cran.rstudio.com/src/contrib/PACKAGES'
#Installing package into ‘C:/Users/inspirion 14a2/Documents/R/win-library/3.4’
#(as ‘lib’ is unspecified)
#Warning in install.packages :
#  unable to access index for repository https://cran.rstudio.com/src/contrib:
#  cannot open URL 'https://cran.rstudio.com/src/contrib/PACKAGES'
############################
# Global option -> Packages->Use secure download method for HTTP.
#You just have to uncheck it