diff --git a/zad2/zad2.gpr b/zad2/zad2.gpr
index 9e47a59..64ed43a 100644
--- a/zad2/zad2.gpr
+++ b/zad2/zad2.gpr
@@ -6,4 +6,8 @@ project Zad2 is
     for Source_Dirs use ("src", Impl);
     for Object_Dir use "target";
 
+    package Builder is
+        for Executable ("main.adb") use "z2";
+    end Builder;
+
 end Zad2;
diff --git a/zad3/Cargo.toml b/zad3/Cargo.toml
index c565456..f7f50dc 100644
--- a/zad3/Cargo.toml
+++ b/zad3/Cargo.toml
@@ -2,3 +2,7 @@
 name = "zad3"
 version = "0.1.0"
 edition = "2021"
+
+[features]
+iter = []
+rec = []
diff --git a/zad3/src/main.rs b/zad3/src/main.rs
index 2d9db80..503f7ad 100644
--- a/zad3/src/main.rs
+++ b/zad3/src/main.rs
@@ -6,29 +6,28 @@ use crate::module::{Module, ModuleIter, ModuleRec};
 
 fn main() {
     let args = env::args().collect::<Vec<_>>();
-    if args.len() != 2 {
-        eprintln!("usage: {} <impl>" /*<a> <b> <c>"*/, args[0]);
+    if args.len() != 4 {
+        eprintln!("usage: {} <a> <b> <c>", args[0]);
         exit(1);
     }
 
-    let r#impl = &args[1];
-    // let a = args[2].parse::<i64>().expect("failed to parse a");
-    // let b = args[3].parse::<i64>().expect("failed to parse b");
-    // let c = args[4].parse::<i64>().expect("failed to parse c");
+    let a = args[1].parse::<i64>().expect("failed to parse a");
+    let b = args[2].parse::<i64>().expect("failed to parse b");
+    let c = args[3].parse::<i64>().expect("failed to parse c");
 
     let module: Box<dyn Module> =
-        if r#impl == "iter" {
+        if cfg!(feature = "iter") {
             Box::new(ModuleIter {})
-        } else if r#impl == "rec" {
+        } else if cfg!(feature = "rec") {
             Box::new(ModuleRec {})
         } else {
             eprintln!("unknown module type");
             exit(1);
         };
 
-    println!("gcd(a, b): {}", module.gcd(10, 5));
-    println!("factorial(a): {}", module.factorial(5));
-    let r = module.diophantine(1027, 712, 1);
+    println!("gcd(a, b): {}", module.gcd(a as u64, b as u64));
+    println!("factorial(a): {}", module.factorial(a as u64));
+    let r = module.diophantine(a, b, c);
     print!("diophantine(a, b, c): ");
     if r.is_none() {
         println!("there's no solution");
diff --git a/zad4/zad4.gpr b/zad4/zad4.gpr
index 66e2379..a8812b7 100644
--- a/zad4/zad4.gpr
+++ b/zad4/zad4.gpr
@@ -8,4 +8,8 @@ project Zad4 is
     for Source_Dirs use ("src", "include", Impl);
     for Object_Dir use "target";
 
+    package Builder is
+        for Executable ("main.c") use "z4";
+    end Builder;
+
 end Zad4;
diff --git a/zad5/zad5.gpr b/zad5/zad5.gpr
index 35a6258..eb62e5d 100644
--- a/zad5/zad5.gpr
+++ b/zad5/zad5.gpr
@@ -8,4 +8,8 @@ project Zad5 is
     for Source_Dirs use ("src", Impl);
     for Object_Dir use "target";
 
+    package Builder is
+        for Executable ("main.adb") use "z5";
+    end Builder;
+
 end Zad5;
diff --git a/zad6/Cargo.toml b/zad6/Cargo.toml
index 2993348..e34f79f 100644
--- a/zad6/Cargo.toml
+++ b/zad6/Cargo.toml
@@ -8,3 +8,7 @@ libc = "0.2.153"
 
 [build-dependencies]
 cc = "1.0.90"
+
+[features]
+iter = []
+rec = []
diff --git a/zad6/build.rs b/zad6/build.rs
index f8602ff..4659dcb 100644
--- a/zad6/build.rs
+++ b/zad6/build.rs
@@ -1,8 +1,16 @@
 extern crate cc;
 
 fn main() {
+    let module =
+        if cfg!(feature = "iter") {
+            "src/mod_iter.c"
+        } else if cfg!(feature = "rec") {
+            "src/mod_rec.c"
+        } else {
+            panic!("unknown module type")
+        };
     cc::Build::new()
-        .file("src/mod_iter.c")
+        .file(module)
         .shared_flag(true)
         .compile("mod.a");
 }
diff --git a/zad6/src/main.rs b/zad6/src/main.rs
index 24d3ad7..b63f4d3 100644
--- a/zad6/src/main.rs
+++ b/zad6/src/main.rs
@@ -1,3 +1,5 @@
+use std::{env, process::exit};
+
 #[repr(C)]
 pub struct Result {
   pub resultExists: libc::c_int,
@@ -15,9 +17,19 @@ extern "C" {
 
 fn main() {
     unsafe {
-        println!("gcd(a, b): {}", gcd(10, 5));
-        println!("factorial(a): {}", factorial(5));
-        let r = diophantine(1027, 712, 1);
+        let args = env::args().collect::<Vec<_>>();
+        if args.len() != 4 {
+            eprintln!("usage: {} <a> <b> <c>", args[0]);
+            exit(1);
+        }
+
+        let a = args[1].parse::<i32>().expect("failed to parse a");
+        let b = args[2].parse::<i32>().expect("failed to parse b");
+        let c = args[3].parse::<i32>().expect("failed to parse c");
+
+        println!("gcd(a, b): {}", gcd(a as u32, b as u32));
+        println!("factorial(a): {}", factorial(a as u32));
+        let r = diophantine(a, b, c);
         print!("diophantine(a, b, c): ");
         if r.resultExists == 0 {
             println!("there's no solution");