/in/foo.c: In function 'Count':
/in/foo.c:5:20: error: 'ij' undeclared (first use in this function)
  for(j = 0; j < n; ij++) {
                    ^~
/in/foo.c:5:20: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c: In function 'main':
/in/foo.c:14:14: error: 'l1' undeclared (first use in this function)
  while((str1[l1++] = getchar()) != '\n');
              ^~
/in/foo.c:15:14: error: 'l2' undeclared (first use in this function)
  while((str1[l2++] = getchar()) != '\n');
              ^~
/in/foo.c:16:21: error: 's1' undeclared (first use in this function)
  int count1 = Count(s1,len1);
                     ^~
/in/foo.c:17:21: error: 's2' undeclared (first use in this function)
  int count2 = Count(s2,len2);
                     ^~