using JuMP
using GLPKMathProgInterface

m = Model(solver = GLPKSolverMIP())

@variable(m, x[1:8] >= 0)
d = [0,2,4,4,3,2,3,0]

#@objective(m, Min, sum(x[i]*d[i] for i = 1:8))
@objective(m, Min, x[8])

@constraint(m, x[4] - x[2] >= d[2])
@constraint(m, x[5] - x[2] >= d[2])
@constraint(m, x[5] - x[3] >= d[3])
@constraint(m, x[6] - x[4] >= d[4])
@constraint(m, x[7] - x[5] >= d[5])
@constraint(m, x[8] - x[6] >= d[6])
@constraint(m, x[8] - x[7] >= d[7])

status = solve(m)

println("Objective = ", getobjectivevalue(m))
println("X = ", getvalue(x))