library(gmp)
library(Rmpfr)

F <- function(N)
{
    a <- as.bigq(c("4", "17 / 4"))
    if (N > 0) for (i in 1:N) a <- c(a[2], 108 - 815 / a[2] + 1500 / prod(a))
    a[1]
}

cat(format(mpfr(F(80), 200), 30), "\n", sep = "")