/in/foo.c: In function 'main':
/in/foo.c:5:2: warning: implicit declaration of function 'gets' [-Wimplicit-function-declaration]
  gets(a);
  ^~~~
/in/foo.c:8:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
     for (j = 0; j < n - 1; j++)
     ^~~
/in/foo.c:18:2: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
  for(i=0; i<n; i++)
  ^~~
/in/foo.c:37:2: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
  printf("%d",-s3);
  ^~~~~~
/in/foo.c:37:2: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:37:2: note: include '<stdio.h>' or provide a declaration of 'printf'
/tmp/ccWtmkcg.o: In function `main':
foo.c:(.text.startup+0x11): warning: the `gets' function is dangerous and should not be used.