How to set the first input constraint

I use acados in MATLAB interface
General MPC finds the optimal solution for the number of Nc. CMPC combines the same model in parallel to obtain an optimal solution considering two scenarios. For this purpose, a constraint is imposed that the values ​​of the first optimal solution are the same.

For CMPC implementation, I need to set the first input constraint

in CMPC (c : contingency, n : nominal)
state X = [Xc;Xn]
input U = [Uc;Un]

Uc = [Uc0, Uc1 … Ucn-1]
Un = [Un0, Un1 … Unn-1]

I want to set the constraint below
Uc0 = Un0
I wonder if there is a way to set it for each horizon.

Looking at acados_ocp_model.m, it seems that opc can make settings for Vu0, but there is no constr_u0.