Question: Error, unable to parse ('local' command)

Hi, i'm working with some spectral acceleration data and i'm having troubles with a 'local' command on a Newmark method code i found on the internet. I'm not a maple expert so i wish someone could help me. i'm ussing maple 2015. Greetings

Newmark=proc(z0,u0,F0);  local beta,  dt, c, kg,a,b, N, i, dF, dz, du, dw, T, m, k ;        dt:=0.01;    T:=4;    N:=T/(dt);    gam:=0.5;    beta:=0.25;      m:=0.320;    k:=435;    c:=2;   z(0):=z0;   u(0):=u0;   F(0):=F0;   w(0):=(1/(m))*(F0-k*z0-c*u0);        t=vector(i,1);    t[1,1]=0;      for i from 2 to N do :  t(i,1)=t(i-1,1)+dt:  end do:           kg:=k+(gam*c)/(beta*dt)+m/(beta*dt*dt);    a:=m/(beta*dt)+(gam*c)/(beta);    b:=  (0.5*m)/(beta)+dt*((0.5*gam)/(beta)-1)*c;       for i from 2 to N do  dF(i):=diff(F,t)+a*u(i)+b*w(i);    dz(i):=(dF(i))/(kg);    du(i):=((gam*dz(i))/(beta*dt))-((gam*u(i-1))/(beta))+dt*(1-gam/(2*beta))*w(i-1);    dw(i):=((du(i))/(beta*dt*dt))-((u(i-1))/(beta*dt))-((w(i-1))/(2*beta));     z(i+1)=dz(i)+z(i);    u(i+1):=du(i)+u(i);    w(i+1):=dw(i)+w(i);     od;       plot([z(i), u(i), w(i)],x=0..50,y=-50..50);       end;