diff --git a/C#/25.1000 FIBONACCI NUMBER/RudaniNishant.CS b/C#/25.1000 FIBONACCI NUMBER/RudaniNishant.CS
new file mode 100644
index 0000000..b8bcdab
--- /dev/null
+++ b/C#/25.1000 FIBONACCI NUMBER/RudaniNishant.CS	
@@ -0,0 +1,14 @@
+// Project Euler Problem No 25
+int i = 0;
+int cnt = 2;
+BigInteger limit = BigInteger.Pow(10, 999);
+BigInteger[] fib = new BigInteger[3];
+ 
+fib[0] = 1;
+fib[2] = 1;
+ 
+while (fib[i] <= limit) {
+    i = (i + 1) % 3;
+    cnt++;
+    fib[i] = fib[(i + 1) % 3] + fib[(i + 2) % 3];
+}
diff --git a/README.md b/README.md
index b794d72..71d5d3a 100644
--- a/README.md
+++ b/README.md
@@ -54,7 +54,7 @@ Happy Contributing! 😃
 | 22 | [Names scores](https://projecteuler.net/problem=22)                          |                    |                    |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |
 | 23 | [Non-abundant sums](https://projecteuler.net/problem=23)                     |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
 | 24 | [Lexicographic permutations](https://projecteuler.net/problem=24)            |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
-| 25 | [1000-digit Fibonacci number](https://projecteuler.net/problem=25)           |                    |                    |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |
+| 25 | [1000-digit Fibonacci number](https://projecteuler.net/problem=25)           |                    |                    |                    | :white_check_mark: |                    |                    |                    | :white_check_mark: |                    |                    |                    |                    |
 | 26 | [Reciprocal cycles](https://projecteuler.net/problem=26)                     |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
 | 27 | [Quadratic primes](https://projecteuler.net/problem=27)                      |                    | :white_check_mark: |                    |                    |                    |                    |                    |                    |                    |                    |                    |                    |
 | 28 | [Number spiral diagonals](https://projecteuler.net/problem=28)               | :white_check_mark: | :white_check_mark: |                    | :white_check_mark: |                    |                    | :white_check_mark: |                    |                    |                    |                    |                    |