该程序的错误原因? .

e=i*i+1/(double)i;

#include<stdio.h>
#include<math.h>
int main()
{
    int m,n,i;
    double sum,e;
    scanf("%d%d",&m,&n);
    for(i=1;i<=n;i++)
    {
        e=i*i+1/(double)i;
        sum+=e;
    }
    printf("sum=%.2lf\n",sum);
    return 0;
}