/in/foo.cc: In function 'int main()':
/in/foo.cc:8:25: error: invalid conversion from 'int' to 'void*' [-fpermissive]
  memset(add,0,sizeof add);
                         ^
In file included from /usr/include/c++/6/cstring:42:0,
                 from /in/foo.cc:4:
/usr/include/string.h:62:14: note:   initializing argument 1 of 'void* memset(void*, int, size_t)'
 extern void *memset (void *__s, int __c, size_t __n) __THROW __nonnull ((1));
              ^~~~~~
/in/foo.cc:13:10: error: invalid types 'int[int]' for array subscript
   b+=s1[a];
          ^
/in/foo.cc:14:3: error: 'c' was not declared in this scope
   c+=s2[a];
   ^
/in/foo.cc:14:10: error: invalid types 'int[int]' for array subscript
   c+=s2[a];
          ^
/in/foo.cc:16:14: error: 'sort' was not declared in this scope
  sort(s3,s3+n);
              ^
/in/foo.cc:17:10: error: 'c' was not declared in this scope
  x=abs(b-c);
          ^
/in/foo.cc:24:11: error: 'X' was not declared in this scope
    if(add>X)
           ^
/in/foo.cc:26:17: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
    else if(add=x){
                 ^