/in/foo.c: In function 'FindMaxs':
/in/foo.c:22:4: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
    if (a[i] = a[j])
    ^~
/in/foo.c:30:9: warning: 'return' with a value, in function returning void
  return n;
         ^
/in/foo.c:14:6: note: declared here
 void FindMaxs(int a[], int b[])
      ^~~~~~~~
/in/foo.c: In function 'main':
/in/foo.c:44:9: error: 'n' undeclared (first use in this function)
  printf(n);
         ^
/in/foo.c:44:9: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:37:21: warning: unused variable 'm' [-Wunused-variable]
  int n1, n2, a1, a2,m;
                     ^
/in/foo.c:37:18: warning: unused variable 'a2' [-Wunused-variable]
  int n1, n2, a1, a2,m;
                  ^~
/in/foo.c:37:14: warning: unused variable 'a1' [-Wunused-variable]
  int n1, n2, a1, a2,m;
              ^~