/in/foo.cc: In function 'int main()':
/in/foo.cc:9:22: error: invalid conversion from 'int' to 'const char*' [-fpermissive]
  printf (rand()%(a+b)+1);
          ~~~~~~~~~~~~^~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:46,
                 from /in/foo.cc:1:
/usr/include/stdio.h:364:12: note:   initializing argument 1 of 'int printf(const char*, ...)'
 extern int printf (const char *__restrict __format, ...);
            ^~~~~~