f1 = -PO4^2+1
f2 = -x1^2-x1
f3 = -x2^2+1
f4 = -O2^2+1
f5 = NO3^2*x4^2+NO3^2*x4+NO3*x4^2+NO3*x4
f6 = -x3^2*x4^2*x5^2*x6+x3^2*x4^2*x5*x6^2-x3^2*x4*x5^2*x6^2-x3*x4^2*x5^2*x6^2-x3^2*x4^2*x5^2+x3^2*x4^2*x5*x6+x3*x4^2*x5^2*x6+x3^2*x4^2*x6^2-x3^2*x4*x5*x6^2+x3*x4^2*x5*x6^2-x3^2*x5^2*x6^2-x4^2*x5^2*x6^2+x3^2*x4^2*x5-x3^2*x4*x5^2+x3*x4^2*x5^2-x3^2*x4^2*x6-x3*x4^2*x5*x6+x3^2*x5^2*x6-x4^2*x5^2*x6-x3*x4^2*x6^2+x3^2*x5*x6^2+x3*x5^2*x6^2+x4*x5^2*x6^2-x3^2*x4^2+x3^2*x4*x5-x3*x4^2*x5+x3*x4*x5^2-x4^2*x5^2+x3*x4^2*x6-x3^2*x5*x6+x4^2*x5*x6-x3*x5^2*x6-x3^2*x6^2+x4^2*x6^2-x3*x5*x6^2+x4*x5*x6^2-x5^2*x6^2-x3^2*x4+x3*x4^2-x3*x4*x5+x4^2*x5-x4*x5^2+x3^2*x6-x4^2*x6+x3*x5*x6+x5^2*x6+x3*x6^2+x5*x6^2+x3*x4-x4^2+x4*x5-x3*x6-x5*x6-x6^2-x4+x6
f7 = -x5^2*x6^2*x7^2+x5^2*x6^2*x7-x5^2*x6*x7^2-x5*x6^2*x7^2-x5^2*x6^2+x5^2*x7^2-x5^2*x7-x6^2*x7+x6*x7^2-x5^2+x6^2-x7^2-x5+x7
f8 = x5^2*x6^2*x13^2*x8^2+x5^2*x6^2*x13^2*x8+x5^2*x6^2*x13*x8^2+x5^2*x6*x13^2*x8^2-x5*x6^2*x13^2*x8^2-x5^2*x6^2*x13^2-x5^2*x6^2*x13*x8-x5^2*x6*x13^2*x8-x5^2*x6*x13*x8^2+x6^2*x13^2*x8^2+x5^2*x6^2*x13+x5^2*x6*x13^2+x5^2*x6*x13*x8-x6^2*x13^2*x8-x6^2*x13*x8^2-x6*x13^2*x8^2-x5^2*x6*x13+x6^2*x13^2+x6^2*x13*x8+x6*x13^2*x8+x5^2*x8^2+x6*x13*x8^2-x6^2*x13-x6*x13^2-x5^2*x8-x6*x13*x8-x5^2+x6*x13-x8^2-x5+x8
f9 = x6^2*x13^2*x7^2*x9-x6^2*x13^2*x7*x9^2-x6^2*x13*x7^2*x9^2-x6*x13^2*x7^2*x9^2-x6^2*x13^2*x7^2-x6^2*x13^2*x9^2+x6^2*x13*x7*x9^2+x6*x13^2*x7*x9^2+x6*x13*x7^2*x9^2-x6^2*x13^2*x9-x6^2*x13*x9^2-x6*x13^2*x9^2-x6*x13*x7*x9^2+x6^2*x13^2+x6*x13*x9^2-x7^2*x9+x7*x9^2+x7^2-x9^2+x9
f10 = x6^2*x13^2*x7^2*x10-x6^2*x13^2*x7*x10^2-x6^2*x13*x7^2*x10^2-x6*x13^2*x7^2*x10^2-x6^2*x13^2*x7^2-x6^2*x13^2*x10^2+x6^2*x13*x7*x10^2+x6*x13^2*x7*x10^2+x6*x13*x7^2*x10^2-x6^2*x13^2*x10-x6^2*x13*x10^2-x6*x13^2*x10^2-x6*x13*x7*x10^2+x6^2*x13^2+x6*x13*x10^2-x7^2*x10+x7*x10^2+x7^2-x10^2+x10
f11 = -x6^2*x13^2*x11^2-x6^2*x13^2*x11-x6^2*x13*x11^2-x6*x13^2*x11^2+x6^2*x13^2+x6*x13*x11^2-x11^2+x11
f12 = NO3^2*x8^2*x12-NO3^2*x8*x12^2-NO3^2*x8^2+NO3*x8^2*x12-NO3^2*x12^2-NO3*x8*x12^2-NO3*x8^2+NO3^2*x12+NO3*x12^2-NO3*x12-x12^2+x12
f13 = -x9^2*x12^2*x13^2-x9^2*x12^2*x13-x9^2*x12*x13^2-x9*x12^2*x13^2+x9^2*x12^2+x9*x12*x13^2-x13^2+x13
f14 = -x10^2*x13^2*x14^2-x10^2*x13^2*x14-x10^2*x13*x14^2-x10*x13^2*x14^2+x10^2*x13^2+x10*x13*x14^2-x14^2+x14
f15 = -x11^2*x14^2*x15^2-x11^2*x14^2*x15-x11^2*x14*x15^2-x11*x14^2*x15^2+x11^2*x14^2+x11*x14*x15^2-x15^2+x15