int_0^1 int_0^(1-x) (1+2e^{-(y-x)^2-(2y+x-1)^2-(y+2x-1)^2}-e^{-2(y-x)^2} - e^{-2(2y+x-1)^2} - e^{-2(y+2x-1)^2}) dy dx