/in/foo.c: In function 'main':
/in/foo.c:33:19: warning: comparison of constant '9' with boolean expression is always true [-Wbool-compare]
    if(!(1<=s[i][j]<=9))  {ok=0;break;}
                   ^~
/in/foo.c:33:10: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
    if(!(1<=s[i][j]<=9))  {ok=0;break;}
         ~^~~~~~~~~
/in/foo.c: In function 'if_dushu':
/in/foo.c:18:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^