diff --git a/Cargo.lock b/Cargo.lock
index b9815a0..85ce5cf 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -45,19 +45,40 @@ checksum = "d8c93436c21e4698bacadf42917db28b23017027a4deccb35dbe47a7e7840123"
 dependencies = [
  "atty",
  "bitflags",
+ "clap_derive",
  "indexmap",
+ "lazy_static",
  "os_str_bytes",
  "strsim",
  "termcolor",
  "textwrap",
 ]
 
+[[package]]
+name = "clap_derive"
+version = "3.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da95d038ede1a964ce99f49cbe27a7fb538d1da595e4b4f70b8c8f338d17bf16"
+dependencies = [
+ "heck",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.11.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ab5ef0d4909ef3724cc8cce6ccc8572c5c817592e9285f5464f8e86f8bd3726e"
 
+[[package]]
+name = "heck"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2540771e65fc8cb83cd6e8a237f70c319bd5c29f78ed1084ba5d50eeac86f7f9"
+
 [[package]]
 name = "hermit-abi"
 version = "0.1.19"
@@ -114,6 +135,48 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.36"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c7342d5883fbccae1cc37a2353b09c87c9b0f3afd73f5fb9bba687a1f733b029"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4af2ec4714533fcdf07e886f17025ace8b997b9ce51204ee69b6da831c3da57"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "ring"
 version = "0.14.6"
@@ -140,6 +203,17 @@ version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
 
+[[package]]
+name = "syn"
+version = "1.0.89"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea297be220d52398dcc07ce15a209fce436d361735ac1db700cab3b6cdfb9f54"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
 [[package]]
 name = "termcolor"
 version = "1.1.3"
@@ -163,12 +237,24 @@ dependencies = [
  "libotp",
 ]
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"
+
 [[package]]
 name = "untrusted"
 version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "55cd1f4b4e96b46aeb8d4855db4a7a9bd96eeeb5c6a1ab54593328761642ce2f"
 
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
 [[package]]
 name = "winapi"
 version = "0.3.9"
diff --git a/Cargo.toml b/Cargo.toml
index b8ddb91..ac227a6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,4 +7,4 @@ edition = "2018"
 
 [dependencies]
 libotp = "0.1.4"
-clap = "3.1.6"                                                                                
+clap = { version = "3.1.6", features = ["derive"] }
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..364fc94 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,31 @@
-fn main() {
-    println!("Hello, world!");
+use clap::Parser;
+
+/// TOTP - One Time Password generator
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+struct Args {
+    /// The secret to use
+    #[clap(short, long)]
+    secret: String,
+
+    /// Interval between two numbers generation
+    #[clap(short, long, default_value_t = 30)]
+    topt_step: u64,
+
+    /// Size of generated secret
+    #[clap(short, long, default_value_t = 6)]
+    len: u32,
+}
+
+fn main() {
+    let args: Args = Args::parse();
+
+    let number = libotp::totp(
+        &args.secret.to_ascii_uppercase(),
+        args.len,
+        args.topt_step,
+        0,
+    );
+
+    println!("Secret len = {}", number.unwrap());
 }