程序出错了，怎么办？

#include<stdio.h>
float fun(int n);
int main()
{
int a;
printf("程序运行结果为：%f", fun(a));
}
float fun(int n)
{
float sum = 0;
for (int i = 200;i <=500;i++)
{
if (i%5==0||i%9==0)
{
sum+=1.0/i;
}
}
return sum;
}

C:\Users\fu15577543725\Desktop\fxh.c(9) : error C2449: found '{' at file scope (missing function header?)

int main()
{
int a;
printf("程序运行结果为：%f", fun(a));
return 0;//加这个试试
}

没有错啊