Need C program suggestions to run into KLEE testing tools

Now, I'm on research study about KLEE testing tool, that we can found on this link. I want to make a research about code coverage that generated with KLEE on non-numerical program.

In the last few times, I have try to generated test case with program replace.c, schedule.c and space.c that can be download from Software Artifact Infractructure, but I don't get the good coverage from it, I don't know maybe I'm wrong or something when doing test.

Usually I test with this command

klee --libc=uclibc --posix-runtime replace.bc --sym-arg 5
klee --libc=uclibc --posix-runtime replace.bc --sym-stdin 10
klee --libc=uclibc --posix-runtime replace.bc --sym-files 1 1024

and sometimes I also try to use Z3 solver, because the default it run with STP solver. Then I run

klee --libc=uclibc --solver-backend=z3 --posix-runtime replace.bc --sym-arg 5

If I run with options --sym-arg I never completed the execution, usually I press ctrl+c to stop, after that I get the coverage only 10.66% and with option --sym-stdin and --sym-files it only get 1.66% coverage. As well as 2 other programs, I also never got a high coverage.

I think may be this is not an appropriate program to run with the KLEE, or may be I forgot some command, please kindly tell me, and also if you have a suggestion C program with non-numeric input, can you share it to me?

Thankyouu