C语言求按顺序排列随机输入的三个数，下面程序出错在哪里

Question

 #include<stdio.h>

   int main()

   {

   void exchange(int x,int y);

   int a,b,c;

   printf("please input three numbers:\n");

   scanf("%d,%d,%d",&a,&b,&c);

   if(a<b)

 exchange(a,b);

  if(a<c)

 exchange(a,c);

  if(b<c)

 exchange(b,c);

  printf("the order is %d,%d,%d\n",a,b,c);

return 0;

  }

 void exchange(int x,int y)

 {int m;

  m=x;

  x=y;

  y=m;

}