绑了 CF 号。

UnexpectedResponse: got an unexpected response when requesting https://codeforces.com/api/user.status: error decoding response body: expected value at line 1 column 1

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod=1e9+7;
inline ll qp(ll a,ll b,ll ret=1) {
	while(b) {if(b&1) ret=ret*a%mod;a=a*a%mod,b>>=1;}
	return ret;
}
int n;
ll f[200010];
int main () {
	cin>>n,f[0]=1;
	for(int i=1;i<=2*n;++i) f[i]=f[i-1]*i%mod;
	cout<<(f[2*n]*qp(f[n]*f[n]%mod,mod-2)-n+mod)%mod;
	return 0;
}