function f=odeplei(~,y)
global zz
f=zeros(28,1);
for i=1:7
    sumx = 0d0;
    sumy = 0d0;
    for j=1:7
        mj = j;
        rij = (y(i)-y(j))^2+(y(i+7)-y(j+7))^2;
        rij32 = rij^(1.5);
        if j~=i
            sumx = sumx+mj*(y(j)-y(i))/rij32;
            sumy = sumy+mj*(y(j+7)-y(i+7))/rij32;
        end
    end
    f(i+14) = sumx;
    f(i+21) = sumy;
end
for i=1:14
    f(i) = y(i+14);
end
zz=zz+1;
