#include<stdio.h>
#define mod 1000000007
#define inv(a) exp(a,mod-2)
typedef long long lld;
lld exp(lld a, lld b){
if(b==0)return 1;
lld k=exp(a, b/2);
k=(k*k)%mod;
if(b%2)k=(k*a)%mod;
return k;
}
lld fac[1001001], rfac[1001001];
void init(){
lld i;
fac[0]=rfac[0]=1;
for(i=1; i<=1000000; i++){
fac[i]=(fac[i-1]*i)%mod;
rfac[i]=inv(fac[i]);
}
}
lld comb(lld a, lld b){
return fac[a]*rfac[b]%mod*rfac[a-b]%mod;
}
lld n, k, dy[1001001];
int main(){
lld i;
init();
scanf("%lld%lld", &n, &k);
dy[0]=1;
for(i=1; i<=n; i++){
dy[i]=dy[i-1]*k%mod;
if(i%2==0){
lld j=i/2;
lld cat=comb(i,j)*inv(j+1)%mod;
cat=(cat*exp(k,j))%mod;
dy[i] = (dy[i]+cat)%mod;
}
}
printf("%lld", dy[n]);
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
511 ms |
24544 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Halted |
0 ms |
0 KB |
- |
