BZOJ4161
http://www.lydsy.com/JudgeOnline/problem.php?id=4161
#include<cstdio>
typedef long long ll;
const int mod=1e9+7;
const ll up=(1ll<<31);
int n,k,ans,x;
int u[4010];
struct poly{
ll a[4010];
poly(){
for(register int i=0;i<k+k-1;++i)
a[i]=0;
}
inline ll &operator[](int x){
return a[x];
}
friend inline poly operator*(poly A,poly B){
register poly ret;
for(register int i=0;i<k;++i)
for(register int j=0;j<k;++j){
ret[i+j]+=1ll*A[i]*B[j];
if(ret[i+j]>=up)
ret[i+j]%=mod;
}
for(register int i=0;i<k+k-1;++i)
ret[i]%=mod;
for(register int i=k+k-2;i>=k;--i){
for(register int j=0;j<k;++j){
ret[i-j-1]+=1ll*ret[i]*u[j];
if(ret[i-j-1]>=up)
ret[i-j-1]%=mod;
}
ret[i]=0;
}
for(register int i=0;i<k;++i)
ret[i]%=mod;
return ret;
}
}f,s;
int main(){
scanf("%d%d",&n,&k);
for(register int i=0;i<k;++i)
scanf("%d",u+i),u[i]=(u[i]%mod+mod)%mod;
for(f[1]=s[0]=1;n;n>>=1,f=f*f)if(n&1)s=s*f;
for(register int i=0;i<k;++i)s[i]%=mod;
for(register int i=0;i<k;++i)scanf("%d",&x),ans=((ans+1ll*x*s[i]%mod)%mod+mod)%mod;
printf("%d\n",ans);
return 0;
}