foo.c: In function 'main':
foo.c:4:5: warning: statement with no effect [-Wunused-value]
     printf"impossible");
     ^
foo.c:4:11: error: expected ';' before string constant
     printf"impossible");
           ^
foo.c:4:23: error: expected statement before ')' token
     printf"impossible");
                       ^
foo.c:5:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^