C# 8.0:
string[] A = Console.ReadLine().Split(' ');
for (int i = 0; i < A.Length; i++) Console.WriteLine($"A[{i + 1}] = {A[i]}");
2 6 -1 64
A[1] = 2
A[2] = 6
A[3] = -1
A[4] = 64
C# 8.0:
string[] A = Console.ReadLine().Split(' ');
for (int i = 0; i < A.Length; i++) Console.WriteLine($"A[{i + 1}] = {A[i]}");
2 6 -1 64
A[1] = 2
A[2] = 6
A[3] = -1
A[4] = 64