# your code goes here
    fIter <- function(n) {
      if ( n < 2 )
        n
      else {
        f <- c(0, 1)
        for (i in 2:n) {
          t <- f[2]
          f[2] <- sum(f)
          f[1] <- t
        }
        f[2]
      }
    }
    fIter(100)