求π值，输出一直为0

Question

#include<stdio.h>
int main(){
int n,i;
long double u,p,pal;
scanf("%d",&n);
i=2;
p=1;
while(i<=2n){
u=((float)i/(i-1))((float)i/(i+1));
p=pu;
i=i+2;
}
pal=2p;
printf("%Lf",pal);
}
为什么输出一直为0

Answer 1

应该是long double的bug，老老实实用double吧