求助一个简单的问题

//#pragma GCC optimize(2)
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define N 200005
#define mod 998244353
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define ld long double
#define ls (rt<<1)
#define rs ((rt<<1)|1)
#define SZ(x) (int)(x.size())
#define debug cout<<endl<<"ff"<<endl
#define YES cout<<"YES"<<endl
#define NO cout<<"NO"<<endl
#define fi first
#define se second
#define INF 1e9
#define pq priority_queue
#define rep(x,a,b) for(int x=a;x<=b;x++)
int qpow(int a,int b){
	int res=1;
	for(;b;b>>=1){
		if(b&1) res=res*a%mod;
		a=a*a%mod;
	}
	return res;
}
/*int fac[N],ifac[N];
int C(int n,int m){
	if(m>n||m<0||n<0) return 0;
	return fac[n]*ifac[n-m]%mod*ifac[m]%mod;
}
void init(){
	fac[0]=1;
	for(int i=1;i<N;i++) fac[i]=fac[i-1]*i%mod;
	ifac[N-1]=qpow(fac[N-1],mod-2);
	for(int i=N-2;i>=0;i--) ifac[i]=ifac[i+1]*(i+1)%mod;
}*/
/*struct node{
	int nxt,to;
}e[N<<1];
int cnt=1,head[N];
inline void add(int x,int y){
	e[++cnt].nxt=head[x];
	head[x]=cnt;
	e[cnt].to=y;
}*/
inline int lowbit(int x){return x&(-x);}
inline int read(){
  int x=0,t=1;char ch=getchar();
  while(ch<'0'||ch>'9'){
    if(ch=='-') t=-1;
    ch=getchar();
  }
    while(ch>='0'&&ch<='9'){
        x=(x<<1)+(x<<3)+(ch-'0');
        ch=getchar();
    }
    return x*t;
}
inline void write(int x){
	if(x<0) putchar('-'),x=-x;
	if(x>=10) write(x/10);
	putchar(x%10+'0');
}
int T,n;
double p[N];
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	p[0]=1;n=1500;
	for(int i=1;i<=n;i++){
		for(int j=0;j<i;j++){
			p[i]=p[i]+p[j]*1.0/(n-j);
		}
	}
	double ans=0;
	for(int j=1;j<=n;j++) ans=ans+p[j];
	cout<<ans<<endl;
	return 0;
}