foo.cc: In function 'int main()':
foo.cc:12:13: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(s+1);
             ^
In file included from /usr/include/stdio.h:862:0,
                 from /usr/include/c++/7/cstdio:42,
                 from foo.cc:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:232:1: note: declared here
 gets (char *__str)
 ^~~~
foo.cc:17:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=1;i<=strlen(s+1);i++) 
             ~^~~~~~~~~~~~~
foo.cc:22:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                    if(strlen(a[k]+1)==i-begin)
                       ~~~~~~~~~~~~~~^~~~~~~~~
foo.cc:24:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                       for(l=1;l<=strlen(a[k]+1);l++,j++)
                               ~^~~~~~~~~~~~~~~~
foo.cc:43:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=2;i<=strlen(s+1);i++)
             ~^~~~~~~~~~~~~
foo.cc:10:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~
foo.cc:12:9: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result [-Wunused-result]
     gets(s+1);
     ~~~~^~~~~
foo.cc:15:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%s",a[i]+1),scanf("%c",&a[i][0]); 
         ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:15:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
/tmp/ccVR0Y6p.o: In function `main':
foo.cc:(.text.startup+0x5c): warning: the `gets' function is dangerous and should not be used.

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。