model {
for (i in 1:20) {Y[i] ~ dgamma(4, 0.04)}
cum[1] <- Y[1]
for (i in 2:20) {
cum[i] <- cum[i - 1] + Y[i]
}
for (i in 1:20) {
cum.step[i] <- i*step(1000 - cum[i])
}
number <- ranked(cum.step[], 20) # maximum number in cum.step
check <- equals(cum.step[20], 0) # always 1 if I=20 big enough
}

   node   mean   sd   MC error   2.5%   median   97.5%   start   sample
   Y[1]   101.1   50.02   0.5408   28.51   93.23   222.2   1   10000
   number   9.631   1.636   0.01503   7.0   10.0   13.0   1   10000

[example-2_5_1-repairs0][example-2_5_1-repairs1]