If |\table x^{2}+x , 3 x-1 , -x+3 ; 2 x+1 , 2+x^{2} , x^{3}-3 ; x-3 , x^{2}+4 , 3 x| =a_{0}+a_{1} x+a_{2} x^{2}+. . .+a_{7} x^{7} then the value of a_{0} is