/in/lab5.c: In function 'main':
/in/lab5.c:204:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             while (j == len && top_signstack != 0)
                      ^~
/in/lab5.c: In function 'compare':
/in/lab5.c:38:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^