#include <stdio.h>
#include <stdlib.h>

#define MOD 1000000007
#define DEBUG 1

int main ( int argc , char * argv[] ) {

    while ( 1 ) {
        long long int a,b;
        long long int result = 0;
        scanf("%lld%lld" , &a,&b);

        if ( a == 0 && b == 0 ) {
            break;
        }

        long long int t = a;
        int i = 0;
        for ( i = 1 ; i <= b ; i++ ) {
            result = (result + t) % MOD;
            t = (t * a) % MOD;
        }

        printf("%lld\n" , result);

    }

    return 0;
}