/in/foo.c: In function 'main':
/in/foo.c:8:13: error: expected identifier or '(' before 'char'
  char s1[N],char s2[N];
             ^~~~
/in/foo.c:9:2: warning: implicit declaration of function 'gets' [-Wimplicit-function-declaration]
  gets(s1);
  ^~~~
/in/foo.c:10:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%s",s2);
  ^~~~~
/in/foo.c:10:2: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:10:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:10:13: error: 's2' undeclared (first use in this function)
  scanf("%s",s2);
             ^~
/in/foo.c:10:13: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c: In function 'Secret':
/in/foo.c:30:2: warning: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
  puts(s2);
  ^~~~