x_{20} = \operatorname{piecewise}(0, t < -1, 0, t < 0, 1, t < 120, 1)\\
x_{21} = x_{20} \cdot k_{35}\\
x_{22} = x_{1}\\
x_{23} = x_{2}\\
x_{24} = x_{3}\\
x_{25} = x_{4}\\
1 \cdot k_{51} \cdot x_{1} + 1 \cdot k_{51} \cdot x_{2} + 1 \cdot k_{51} \cdot x_{3} + 1 \cdot k_{51} \cdot x_{4} + 1 \cdot k_{51} \cdot x_{5} + 1 \cdot k_{51} \cdot x_{7} + 1 \cdot k_{51} \cdot x_{8} + 1 \cdot k_{52} \cdot x_{9} + 1 \cdot k_{52} \cdot x_{10} + 1 \cdot k_{52} \cdot x_{11} + 1 \cdot k_{52} \cdot x_{12} + 1 \cdot k_{52} \cdot x_{13} + 1 \cdot k_{52} \cdot x_{15} + 1 \cdot k_{52} \cdot x_{16} + 1 \cdot k_{52} \cdot x_{17} = k_{51} \cdot k_{53} + k_{52} \cdot k_{54}\\
1 \cdot k_{51} \cdot x_{6} + 1 \cdot k_{51} \cdot x_{7} + 1 \cdot k_{51} \cdot x_{8} = k_{51} \cdot k_{55}\\
1 \cdot k_{52} \cdot x_{14} + 1 \cdot k_{52} \cdot x_{15} + 1 \cdot k_{52} \cdot x_{16} + 1 \cdot k_{52} \cdot x_{17} = k_{52} \cdot k_{56}