/in/foo.c: In function 'main':
/in/foo.c:11:5: error: invalid suffix "x" on integer constant
   x=3x+1;
     ^~
/in/foo.c:14:6: error: expected ';' before ')' token
   i++)
      ^
/in/foo.c:14:6: error: expected statement before ')' token
/in/foo.c:17:1: error: expected declaration or statement at end of input
 }
 ^