这是我用vc++写的程序，照着书打的
#include <stdio.h>
main()
{
    int a,b,c,d;
    printf("Enter three integers:");
    scanf(" %d,%d,%d ",&a,&b,&c);
    d=max (a,b,c);
    printf("max is %d \n",d);
}

    int max(int x,int y, intz)
    {
        int w;
        if(x>=y)
            if(x>=z)
                w=x;
            else
                w=z;
            else
                if(y>=z)
                    w=y;
                else
                    w=z;
                return w;

}

这是提示的错误，我不知道怎么改，我对照下，和书上的一模一样啊。
error C2065: 'max' : undeclared identifier
warning C4508: 'main' : function should return a value; 'void' return type assumed
error C2373: 'max' : redefinition; different type modifiers
请大家帮帮我

谢谢啊，请告诉我具体该改那块好吗