integration problem (積分に関する問題)

I want to calculate these formula in matlab,so I wrote a program as below. But in my program, calclation stopped in pint1.How can I fix the problem?

%% Adaptive Filters
clear all;

%% parameters
a = 0.2;      %field loss coefficient α
y = 1.3;       % fiber non-linearity coefficient　γ
Ns = 20;        %number of span
Ls = 100;       %span length         
b2 = 20.7;     %dispersion coefficient β2
%% formula of ρ
syms z f f1 f2;
assume(z>0);
PI = pi;
Le = (abs((int(exp(2*z-2*a*z),z,0,Ls))))^2 ;%square of span effective length
fa = exp(1j*4*PI^2*(f1-f)*(f2-f)*b2*z); %third element of integration about z in formula about ρ
p = (abs(int(exp(2*z-2*a*z)*fa,z,0,Ls)))^2/Le; %ρ
%%formula of NLI
pint1 = int(p,f1,-0.5,0.5);%integration about f1
pint2 = int(pint1,f2,-0.5,0.5);%integration about f2
NLI = (16/27)*y^2*Le*pint2; % NLI of 1span

condition: β3=0, g(ε)=1, Gwdm(f1)=Gwdm(f2)=Gwdm(f1+f2-f)=1

Thank you.