https://www.nowcoder.com/acm/contest/129/A
#include<bits/stdc++.h> using namespace std; typedef long long LL; int maxn=1000+10; LL mod =1e9+7; LL comb[1010][1010]; void init() { for(int i=0;i<maxn;i++) { comb[i][0]=comb[i][i]=1; for(int j=1;j<i;j++) { comb[i][j]=comb[i-1][j-1]+comb[i-1][j]; comb[i][j]%=mod; } } } int main() { init(); int n; scanf("%d",&n); n--; long long ans=0; for(int i=0;i<=n/4;i++) { ans=ans+comb[n][2*i]%mod*comb[n-2*i][2*i]%mod; ans=ans%mod; } printf("%lld\n",ans); return 0; }