/in/foo.cc: In function 'int main()':
/in/foo.cc:100:13: error: invalid conversion from 'clock_t (*)() throw () {aka long int (*)() throw ()}' to 'unsigned int' [-fpermissive]
  srand(clock);
             ^
In file included from /usr/include/c++/6/cstdlib:75:0,
                 from /in/foo.cc:4:
/usr/include/stdlib.h:337:13: note:   initializing argument 1 of 'void srand(unsigned int)'
 extern void srand (unsigned int __seed) __THROW;
             ^~~~~