How to change the duty cycle of a square wave without introducing any change in the pulse generaror in MATLAB simulink?

Question

I have four square waves S1, S2, S3 and S4. All have 50% duty cycle. When S1 is on S2 is off (vice versa) and when S4 is on S3 is off (vice versa). I want to change the duty cycle of S1 and S3 to more than 50 % and the duty cycle of S2 and S4 to less than 50% of the period (as shown in the figure), without introducing any change in the pulse generator, i.e. the change has to be done outside the pulse generator.How do I do it in MATLAB simulink? Image of the pulses in required fashion//Image of the pulse generator block

The pulses are generated using a sawtooth generator, hit crossing block and SR flip-flop.