c_1 = 0
c_2 = 0
c_3 = 0
c_4 = 0
c_5 = 0
c_6 = 0
c_7 = 0
c_8 = 0
c_9 = 0
c_{10} = 0
c_{11} = 0
c_{12} = 0
c_{13} = 0
c_{14} = 0
c_{15} = 0
c_{16} = 0
c_{17} = 0
c_{18} = 0