diff --git a/2019/07/src/main.rs b/2019/07/src/main.rs
index b92fce7..11f68a9 100644
--- a/2019/07/src/main.rs
+++ b/2019/07/src/main.rs
@@ -2,6 +2,6 @@ use intcode::*;
 
 pub fn main() {
     let input = read_input();
-    println!("Part 1: {}", find_max(0..5, &input));
-    println!("Part 2: {}", find_max(5..10, &input));
+    println!("Part 1: {}", find_max(0..5, &input).unwrap());
+    println!("Part 2: {}", find_max(5..10, &input).unwrap());
 }
diff --git a/2019/intcode/src/lib.rs b/2019/intcode/src/lib.rs
index d1294ab..2ff62c5 100644
--- a/2019/intcode/src/lib.rs
+++ b/2019/intcode/src/lib.rs
@@ -1,4 +1,5 @@
 use itertools::Itertools;
+use std::convert::TryFrom;
 use std::io::{self, BufRead};
 use std::ops::Range;
 
@@ -156,30 +157,37 @@ fn execute(op: Operation, input: &mut Vec<i64>, pos: &mut i64) -> Option<i64> {
     }
 }
 
-pub fn find_max(range: Range<i64>, input: &Vec<i64>) -> i64 {
-    range
-        .permutations(5)
-        .scan(0, |&mut mut acc, amps| {
-            let mut machines: Vec<_> = amps
-                .into_iter()
-                .map(|amp| Machine {
-                    tape: input.clone(),
-                    pos: 0,
-                    params: vec![amp],
-                })
-                .collect();
-            for state in (0..5).cycle() {
-                let mut machine = machines.get_mut(state).unwrap();
-                machine.params.insert(0, acc);
-                match execute_machine(&mut machine) {
-                    Err(output) => acc = output,
-                    Ok(_) => break,
-                }
-            }
-            Some(acc)
+pub fn run_for_input(input: &Vec<i64>, acc: &mut i64, amps: Vec<i64>) -> i64 {
+    let mut machines: Vec<_> = amps
+        .into_iter()
+        .map(|amp| Machine {
+            tape: input.clone(),
+            pos: 0,
+            params: vec![amp],
+        })
+        .collect();
+    for state in (0..machines.len()).cycle() {
+        let mut machine = machines.get_mut(state).unwrap();
+        machine.params.insert(0, *acc);
+        match execute_machine(&mut machine) {
+            Err(output) => *acc = output,
+            Ok(_) => break,
+        }
+    }
+    *acc
+}
+
+pub fn find_max(range: Range<i64>, input: &Vec<i64>) -> Option<i64> {
+    usize::try_from(range.end - range.start)
+        .ok()
+        .and_then(|len| {
+            range
+                .permutations(len)
+                .scan(0, |&mut mut acc, amps| {
+                    Some(run_for_input(input, &mut acc, amps))
+                })
+                .max()
         })
-        .max()
-        .unwrap()
 }
 
 fn execute_machine(machine: &mut Machine) -> Result<i64, i64> {
diff --git a/2019/intcode/src/tests.rs b/2019/intcode/src/tests.rs
index 2a5bf3a..39d6cdc 100644
--- a/2019/intcode/src/tests.rs
+++ b/2019/intcode/src/tests.rs
@@ -12,21 +12,23 @@ fn test_find_max() {
             0..5,
             &parse_test_input("3,15,3,16,1002,16,10,16,1,16,15,15,4,15,99,0,0")
         ),
-        43210
+        Some(43210)
     );
     assert_eq!(
         find_max(
             0..5,
-            &parse_test_input("3,23,3,24,1002,24,10,24,1002,23,-1,23,101,5,23,23,1,24,23,23,4,23,99,0,0")
+            &parse_test_input(
+                "3,23,3,24,1002,24,10,24,1002,23,-1,23,101,5,23,23,1,24,23,23,4,23,99,0,0"
+            )
         ),
-        54321
+        Some(54321)
     );
     assert_eq!(
         find_max(
             0..5,
             &parse_test_input("3,31,3,32,1002,32,10,32,1001,31,-2,31,1007,31,0,33,1002,33,7,33,1,33,31,31,1,32,31,31,4,31,99,0,0,0")
         ),
-        65210
+        Some(65210)
     );
 }
 
@@ -37,13 +39,13 @@ fn test_find_max_with_loops() {
             5..10,
             &parse_test_input("3,26,1001,26,-4,26,3,27,1002,27,2,27,1,27,26,27,4,27,1001,28,-1,28,1005,28,6,99,0,0,5")
         ),
-        139629729
+        Some(139629729)
     );
     assert_eq!(
         find_max(
             5..10,
             &parse_test_input("3,52,1001,52,-5,52,3,53,1,52,56,54,1007,54,5,55,1005,55,26,1001,54,-5,54,1105,1,12,1,53,54,53,1008,54,0,55,1001,55,1,55,2,53,55,53,4,53,1001,56,-1,56,1005,56,6,99,0,0,0,0,10")
         ),
-        18216
+        Some(18216)
     );
 }