代码如下，信奥赛通过的代码搬过来就 wa 了

#include<cstdio>
#include<cmath>

int main()
{
    double x;
    int n;
    scanf("%lf %d",&x,&n);
    double res = 1.0 + x;
    for (int i = n; i > 1; i--)
    {
        res += pow(x,i);
    }
    printf("%.2f",res);

    return 0;
}