Single Mass Oscillator. ODE with more conditions than variables

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i have the following ODE of a single mass oscillator with a spring and a damper:

$m*\ddot{s}=-d*\dot{s}-c*s+m*g$

where $m = 5$, $g=10$
$c$ & $d$ are variable

The ODE is now :

$\ddot{s}=-\frac{d}{5}*\dot{s}-\frac{c}{5}*s+10$

I have 2 intitial conditions that have to apply:

$s(0)=0$

$\dot{s}(0)=0$

Now to my question: If I calculate the solution of the oscillation (e.g. with Matlab) I get

$s(t,c,d)$ which is still depending on the variables $c$ an $d$

Further i can calculate the derivatives of the solution depending on $c$ and $d$

$\dot{s}(t,c,d)$

$\ddot{s}(t,c,d)$

My problem is, that i have 3 conditions for 2 unknown variables, which makes the linear system of equations needed to solve for $c$ and $d$ overdetermined.

$s(t_{max})=s_{max}$

$\dot{s}(\ddot{s}=0)=\dot{s}_{max}$

$\dot{s}(t_{max})=0$

How do I solve for $c$ and $d$ so that all the conditions including the initial conditions are met and valid for this ODE?