def f(p):n=len(p);p=p+p[:1];i=s=0;exec'd=(p[i].conjugate()*p[i+1]).imag;s+=d;p[i]=(p[i]+p[i+1])*d;i+=1;'*n;print sum(p[:n])/s/3
f([0, 1, 1+1j, 0+1j])
f([-15.21+0.8j, 10.1-0.3j, -0.07+23.55j])
f([-39-55.94j, -56.08-4.73j, -72.64+12.12j, -31.04+53.58j, -30.36+28.29j, 17.96+59.17j, 0, 10, 20, 148.63+114.32j, 8.06-41.04j, -41.25+34.43j])
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