My earlier Euler program and one using BLOCK

```
program main
! simulate Euler's number e
implicit none
integer, parameter :: nsim = 10000000, niter = 10
integer :: i,iter,nsum(nsim)
call random_seed()
do iter=1,niter
do i=1,nsim
block
real :: xsum,xran
integer :: j
xsum = 0.0
j = 0
do
j = j + 1
call random_number(xran)
xsum = xsum + xran
if (xsum > 1.0) exit
end do
nsum(i) = j
end block
end do
print*,sum(nsum)/real(nsim),minval(nsum),maxval(nsum)
end do
print*,exp(1.0)," true"
end program main
```

take the same time using gfortran -O2.