#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define popcount __builtin_popcount using namespace std; typedef long long int ll; typedef pair P; const ll MOD=1e9+7; ll powmod(ll a, ll k){ ll ap=a, ans=1; while(k){ if(k&1){ ans*=ap; ans%=MOD; } ap=ap*ap; ap%=MOD; k>>=1; } return ans; } ll inv(ll a){ return powmod(a, MOD-2); } ll f[200020], invf[200020]; void fac(int n){ f[0]=1; for(ll i=1; i<=n; i++) f[i]=f[i-1]*i%MOD; invf[n]=inv(f[n]); for(ll i=n-1; i>=0; i--) invf[i]=invf[i+1]*(i+1)%MOD; } ll comb(int x, int y){ if(!(0<=y && y<=x)) return 0; return f[x]*invf[y]%MOD*invf[x-y]%MOD; } struct node{ node* nxt[27]; int cnt; node(){ fill(nxt, nxt+27, nullptr); cnt=0; } }; void add(node* t, string p){ node* t0=t; for(int i=0; inxt[p[i]-'a']){ t0->nxt[p[i]-'a']=new node(); } t0=t0->nxt[p[i]-'a']; t0->cnt++; } } int n, k; ll c[202020]; void dfs(node* t, int d){ if(!t) return; int x=t->cnt; if(d && k>=x) (c[d]+=comb(k, x)*f[x]%MOD*comb(n-x, k-x)%MOD*f[k-x])%=MOD; for(int i=0; i<=26; i++){ if(!t->nxt[i]) continue; dfs(t->nxt[i], d+1); } } int main() { cin>>n; node t; int m=0; string s[2020]; for(int i=0; i>s[i]; m=max(m, (int)s[i].size()); } for(int i=0; i