/in/foo.c: In function 'main':
/in/foo.c:4:6: error: array size missing in 'S'
  int S[],i=0,j=0;k=1;
      ^
/in/foo.c:4:18: error: 'k' undeclared (first use in this function)
  int S[],i=0,j=0;k=1;
                  ^
/in/foo.c:4:18: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:11:2: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  if(A[j]=S[i])
  ^~
/in/foo.c:12:3: error: 'K' undeclared (first use in this function)
   K=i+1-j;
   ^