/in/foo.c: In function 'main':
/in/foo.c:16:21: error: 's1' undeclared (first use in this function)
  int count1 = Count(s1,len1);
                     ^~
/in/foo.c:16:21: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:17:21: error: 's2' undeclared (first use in this function)
  int count2 = Count(s2,len2);
                     ^~