/in/foo.c: In function 'main':
/in/foo.c:51:17: warning: format '%s' expects argument of type 'char *', but argument 3 has type 'char (*)[10001]' [-Wformat=]
     scanf("%d\n%s\n%s\n%s", &l, &b[0], &b[1], &b[2]);
                 ^
/in/foo.c:51:21: warning: format '%s' expects argument of type 'char *', but argument 4 has type 'char (*)[10001]' [-Wformat=]
     scanf("%d\n%s\n%s\n%s", &l, &b[0], &b[1], &b[2]);
                     ^
/in/foo.c:51:25: warning: format '%s' expects argument of type 'char *', but argument 5 has type 'char (*)[10001]' [-Wformat=]
     scanf("%d\n%s\n%s\n%s", &l, &b[0], &b[1], &b[2]);
                         ^
/in/foo.c:54:9: warning: implicit declaration of function 'strrev' [-Wimplicit-function-declaration]
         strrev(b[0]);
         ^~~~~~
/tmp/ccTc49DJ.o: In function `main':
foo.c:(.text.startup+0x7e): undefined reference to `strrev'
foo.c:(.text.startup+0xa3): undefined reference to `strrev'
foo.c:(.text.startup+0xc8): undefined reference to `strrev'
collect2: error: ld returned 1 exit status