19之前答案还对，19开始加法加出错误了```c #include<stdio.h> int main() { int n; scanf("%d",&n); double a[51],sum; a[0]=1; sum=0; for(int i=1;i<=n;i++) { a[i]=i*a[i-1]; sum=sum+a[i]; //printf("a[%d]=%lf\n",i,a[i]); } printf("%.0lf\n",sum); return 0; }