有如下程序：#includeusingnamespacestd;voidf(int&x，int&y){intz=x;x=y;y=z;}voidf(intx;inty){intz=x;x=y;y=z;}intmain(){intx=，y=;f(x，y);f(x，y);cout<<x<<endl;return;}运行时的输出结果是