code not compiling, cant find the problem?

Question

using System;

namespace HelloWorld
{
class Program
{
static void Main(string[] args)
{
int sum = 0;

for(int sum = 0; i < 5; i++)
{
sum += i;
}

for(int i > 0; i--)
{
sum += i;
}
Console.WriteLine(sum);
}
}
}