function [ x, y, t ] = RK_pray_pred( t0, tfin, N, x0, y0, a, b, c, d )

t=linspace(t0,tfin,N);
dt=t(2)-t(1);

x(1)=x0;
y(1)=y0;

for i=1:N-1
    xm(i)=x(i) + (dt/2)*( a*x(i)-b*x(i)*y(i) );
    ym(i)=y(i) + (dt/2)*( -c*y(i)+d*x(i)*y(i) );
    
    x(i+1)=x(i) + dt*( a*xm(i)-b*xm(i)*ym(i) );
    y(i+1)=y(i) + dt*( -c*ym(i)+d*xm(i)*ym(i) );
end

end

