OJ-Problems-Source/HDOJ/2086_autoAC.cpp

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#include<stdio.h>
int main()
{
int n,i;
double a1,an,c[3001],s,x;
while(~scanf("%d",&n))
{
scanf("%lf%lf",&a1,&an);
for(i=1;i<=n;i++)
scanf("%lf",&c[i]);
s=n*a1+an;x=0;
for(i=1;i<=n;i++)
x+=(n-i+1)*c[i];
s=(s-2*x)/(n+1);
printf("%.2lf\n",s);
}
return 0;
}