838D - Airplane Arrangements - CodeForces Solution

#include <bits/stdc++.h>

using namespace std;

inline int read()
{
	int x=0;bool f=0;char ch=getchar();
	while(ch<'0' || ch>'9') {if(ch=='-') f=1;ch=getchar();}
	while(ch>='0' && ch<='9') x=(x<<3)+(x<<1)+(ch^48),ch=getchar();
	return f?-x:x;
}

#define x first
#define y second

typedef pair<int,int> PII;
typedef long long LL;
const int N=1e6+10,MOD=1e9+7;

int n,m;

int qmi(int x,int k)
{
	int res=1;
	while(k){
		if(k&1) res=res*1ll*x%MOD;
		x=x*1ll*x%MOD,k>>=1;
	}
	return res;
}

int main()
{
	n=read(),m=read();
	printf("%d\n",qmi(2,m)*1ll*(n-m+1)%MOD*qmi(n+1,m-1)%MOD);
	
	return 0;
}