diff --git a/voltage_divider.py b/voltage_divider.py
index 1b981b3..5e4dc0a 100644
--- a/voltage_divider.py
+++ b/voltage_divider.py
@@ -20,9 +20,19 @@ def find_bests(desired_ratio, resistors):
     for i, (error, R1, R2, ratio) in enumerate(candidates, start=1):
         print(f"{i}. R1 = {R1} Ω, R2 = {R2} Ω  -> ratio = {ratio:.6f}, error = {error:.6e}")
 
-if __name__ == '__main__':
-    raw_input = input("Enter resistor values (floats) separated by spaces or commas: ")
-    resistors = [float(x) for x in raw_input.replace(',', ' ').split() if x.strip()]
+def parse_resistors(raw_input):
+    values = []
+    for token in raw_input.replace(',', ' ').split():
+        try:
+            v = float(token)
+            if v <= 0:
+                raise ValueError
+            values.append(v)
+        except ValueError:
+            raise ValueError(f"Invalid resistor value '{token}'.")
+    return values
+
+def get_ratio():
     while True:
         try:
             desired_ratio = float(input("Enter desired ratio (0<ratio<=1): "))
@@ -32,6 +42,20 @@ if __name__ == '__main__':
                 print("Invalid ratio.")
         except ValueError:
             print("Invalid input.")
+    return desired_ratio
 
+def get_inputs():
+    raw_input_resistors = input("Enter resistor values (floats) separated by spaces or commas: ")
+    resistors = parse_resistors(raw_input_resistors)
+    desired_ratio = get_ratio()
+
+    return (resistors, desired_ratio)
+
+if __name__ == '__main__':
+    try:
+        resistors, desired_ratio = get_inputs()
+    except ValueError as e:
+        print(e)
+        exit(1)
     find_bests(desired_ratio, resistors)