Codeforces Round #554 (Div. 2) D

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int maxn=2e3+5;
const int mod=1e9+7;
int f[maxn][maxn],n;
int main()
{
    cin>>n;
	f[1][1]=1;
	for(int i=1;i<=n+1;++i)
		for(int j=1;j<=i;++j)
			f[i][j]+=f[i][j-1]+f[i-1][j],
			f[i][j]%=mod;
	ll ans=0;
	for(int i=1;i<=n+1;++i)
		for(int j=1;j<=i;++j)
			if(i+j&1)
				ans+=f[i][j],
				ans%=mod;
	
	cout<<ans;
	return 0;
	
}