¡¾CSU 1556¡¿Pseudoprime numbers

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Description

?Jerry is caught by Tom. He was penned up in one room with a door, which only can be opened by its code. The code is the answer of the sum of the sequence of number written on the door. The type of the sequence of number is

1^m + 2^m + 3^m + ¡­¡­ + n^m

But Jerry¡¯s mathematics is poor, help him to escape from the room.

Input

?There are some cases (about 500). For each case, there are two integer numbers n, m describe as above ( 1 <= n < 1 000 000, 1 <= m < 1000).

Output

?For each case, you program will output the answer of the sum of the sequence of number (mod?1e9+7).

Sample Input

4 1
5 1
4 2
5 2
4 3

Sample Output

10
15
30
55
100

ÌâÒ⣺Çó1^m + 2^m + 3^m + ¡­¡­ + n^m ?(mod?1e9+7)

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#include<stdio.h>
#define M 1000000007
long long qpow(long long a,long long m)//¿ìËÙÃÝ
{
    long long ans=1,k=a;
    while(m)
    {
        if(m&1)
            ans=(ans*k)%M;
        k=(k*k)%M;
        m>>=1;
    }
    return ans;
}
int main()
{
    long long n,m,ans;
    while(scanf("%lld%lld",&n,&m)!=EOF)
    {
        ans=0;
        for(int i=1; i<=n; i++)
            ans+=qpow(i,m)%M;//ÕâÀïmodÒ»ÏÂ
        printf("%lld\n",ans%M);//ÕâÀïmodÒ»ÏÂ
    }
    return 0;
}