10523.cpp

#include <cstdio>
#include <cstring>

#define BASE 1000000000

using namespace std;

struct bignum {
    int  l;
    long d[30];
} sum, base;

int main(void)
{
    int n, a, i, j;

    while (scanf("%d %d", &n, &a) != EOF) {
        memset(sum.d, 0, sizeof(sum.d));
        sum.l = 1;
        memset(base.d, 0, sizeof(base.d));
        base.l    = 1;
        base.d[0] = a;

        for (i = 1; i <= n; ++i) {
            for (j = 0; j < base.l; ++j) {
                sum.d[j] += base.d[j] * i;
                base.d[j] *= a;
            }
            for (j = 0; j < base.l; ++j) {
                base.d[j + 1] += base.d[j] / BASE;
                base.d[j] %= BASE;
            }
            if (base.d[j] > 0) ++base.l;
            for (j = 0; j < sum.l; ++j) {
                sum.d[j + 1] += sum.d[j] / BASE;
                sum.d[j] %= BASE;
            }
            if (sum.d[j] > 0) ++sum.l;
        }

        i = sum.l - 1;
        printf("%ld", sum.d[i]);
        while (--i > -1)
            printf("%09ld", sum.d[i]);
        printf("\n");
    }

    return 0;
}