void pjf()
{float are[n];int i,j;
float temp;
for(i=0;i<n;i++)
are[i]=(a[i].y+a[i].s+a[i].w)/3.0;
struct stu t;

for(i=0;i<n;i++)
for(j=i;j<n;j++)
if(are[i]<are[j])
{
temp = are[i];
are[i]= are[j];
are[j] = temp;

t=a[i];
a[i]=a[j];a[j]=t;}
for(i=0;i<3;i++)
{printf("%-5d",a[i].xh);
puts(a[i].a);
printf("%5d%5d%5d\n",a[i].y,a[i].s,a[i].w);}}