Submission #19956

#TimeUsernameProblemLanguageResultExecution timeMemory
19956suzy괄호 (kriii4_R)C++14
0 / 100
439 ms16708 KiB
#include <stdio.h>

#define MOD 1000000007

typedef long long lli;

lli f[1000001];
lli inv[1000001];

lli p(lli a, lli x) {
	if(x==0) return 1;
	if(x%2) return a*p(a,x-1)%MOD;
	else { lli m=p(a,x/2); return m*m%MOD; }
}

int main() {
	int n, k;
	scanf("%d %d",&n,&k);
	f[0]=f[1]=1;
	for(long long i=2;i<=1000000;i++)
		f[i]=f[i-1]*i%MOD;
	for(int i=0;i<=1000000;i++)
		inv[i]=p(f[i],MOD-2);
	lli res=0;
	for(lli l=n/2+n%2;l<=n;l++) {
		lli t=f[l]*inv[n-l]%MOD;
		t=t*inv[2*l-n]%MOD;
		t=t*p(k,l)%MOD;
		res+=t; res%=MOD;
	}
	printf("%lld",res);
}
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