diff --git a/cairo_program/src/integer.cairo b/cairo_program/src/integer.cairo
index 9501eca..da92c81 100644
--- a/cairo_program/src/integer.cairo
+++ b/cairo_program/src/integer.cairo
@@ -18,3 +18,5 @@ fn add_num(x: u8, y: u8) -> u8 {
 fn sub_num(x: u8, y: u8) -> u8 {
     return x - y;
 }
+
+
diff --git a/starknet_contracts/Scarb.toml b/starknet_contracts/Scarb.toml
index 29cf20f..c668332 100644
--- a/starknet_contracts/Scarb.toml
+++ b/starknet_contracts/Scarb.toml
@@ -12,6 +12,9 @@ starknet = "2.18.0"
 snforge_std = "0.56.0"
 assert_macros = "2.18.0"
 
+[sncast.sepolia]
+rpc_url = "https://starknet-sepolia.g.alchemy.com/starknet/version/rpc/v0_10/G4jDk3UFm0zD_87h21VJH"
+
 [[target.starknet-contract]]
 sierra = true
 
diff --git a/starknet_contracts/snfoundry.toml b/starknet_contracts/snfoundry.toml
index c06aab7..caba84c 100644
--- a/starknet_contracts/snfoundry.toml
+++ b/starknet_contracts/snfoundry.toml
@@ -9,3 +9,6 @@
 # wait-params = { timeout = 300, retry-interval = 10 }     # Wait for submitted transaction parameters
 # block-explorer = "StarkScan"                             # Block explorer service used to display links to transaction details
 # show-explorer-links = true                               # Print links pointing to pages with transaction details in the chosen block explorer
+
+[sncast.sepolia]
+account = "_hen-account1"
\ No newline at end of file
diff --git a/starknet_contracts/src/arithmetic.cairo b/starknet_contracts/src/arithmetic.cairo
new file mode 100644
index 0000000..5a71dda
--- /dev/null
+++ b/starknet_contracts/src/arithmetic.cairo
@@ -0,0 +1,29 @@
+
+pub fn add(x: u32, y: u32) -> u32 {
+    x + y
+}
+
+pub fn subtract(x: u32, y: u32) -> u32{
+    assert(x > 0, 'x must be greater than 0');
+    assert(x > y, 'y cant be greater than x');
+    x - y
+}
+
+pub fn multiply(x: u32, y: u32) -> u32 {
+    let x_u256: u256 = x.into();
+    let y_u256: u256 = y.into();
+
+    let result = x_u256 * y_u256;
+    assert(result <= 255, 'Overflow');
+    result.try_into().unwrap()
+}
+
+pub fn divisio(x: u32, y:u32) -> u32 {
+    assert(y != 0, 'Undefined');
+    let x_u256: u256 = x.into();
+    let y_u256: u256 = y.into();
+
+    let result = x_u256 / y_u256;
+    assert(result <= 255, 'Overflow');
+    result.try_into().unwrap()
+}
\ No newline at end of file
diff --git a/starknet_contracts/src/lib.cairo b/starknet_contracts/src/lib.cairo
index f1b82bb..635e290 100644
--- a/starknet_contracts/src/lib.cairo
+++ b/starknet_contracts/src/lib.cairo
@@ -1,32 +1,73 @@
+mod arithmetic;
+
+use arithmetic::{add, subtract};
+use starknet::{ContractAddress, get_caller_address};
+
 /// Interface representing `HelloContract`.
 /// This interface allows modification and retrieval of the contract's storage count.
 #[starknet::interface]
 pub trait ICounter<T> {
+    fn change_owner(ref self: T, new_owner: ContractAddress);
     /// Increase count.
     fn increase_count(ref self: T, amount: u32);
     /// Retrieve count.
     fn get_count(self: @T) -> u32;
+    fn reduce_count(ref self: T, amount: u32);
+    fn only_owner(self: @T);
+    fn get_owner(self: @T) -> ContractAddress;
 }
 
 /// Simple contract for managing count.
 #[starknet::contract]
 mod Counter {
-    use starknet::storage::{StoragePointerReadAccess, StoragePointerWriteAccess};
+    use crate::ICounter;
+use starknet::storage::{StoragePointerReadAccess, StoragePointerWriteAccess};
+    use super::{add, subtract};
+    use super::{ContractAddress, get_caller_address};
 
     #[storage]
     struct Storage {
         count: u32,
+        owner: ContractAddress
     }
 
+    #[constructor]
+    fn constructor(ref self: ContractState, owner: ContractAddress) {
+        self.owner.write(owner);
+    }
+    
     #[abi(embed_v0)]
     impl CounterImpl of super::ICounter<ContractState> {
+        
+        fn only_owner(self: @ContractState) {
+            let caller = get_caller_address();
+            assert(caller == self.owner.read(), 'Not owner');
+        }
+        
+        fn change_owner(ref self: ContractState, new_owner: ContractAddress) {
+            self.only_owner();
+            self.owner.write(new_owner);
+        } 
+
         fn increase_count(ref self: ContractState, amount: u32) {
+            self.only_owner();
             assert(amount != 0, 'Amount cannot be 0');
-            self.count.write(self.count.read() + amount);
+            self.count.write(add(self.count.read(), amount));
+        }
+
+        fn reduce_count(ref self: ContractState, amount: u32) {
+            self.only_owner();
+            assert(amount != 0, 'Amount cannot be 0');
+            self.count.write(subtract(self.count.read(), amount));
         }
 
         fn get_count(self: @ContractState) -> u32 {
             self.count.read()
         }
+
+        fn get_owner(self: @ContractState) -> ContractAddress {
+            self.owner.read()
+        }
+
     }
 }