diff --git a/src/day01.rs b/src/day01.rs
index a376006..78fb353 100644
--- a/src/day01.rs
+++ b/src/day01.rs
@@ -1,12 +1,12 @@
-use crate::utils;
+use crate::utils::read_data;
 use anyhow::Result;
 
-fn count_incrementing_windows(window: usize, v: &[i64]) -> usize {
+fn count_incrementing_windows(window: usize, v: &[usize]) -> usize {
     v[window..].iter().zip(v).filter(|(b, a)| b > a).count()
 }
 
 pub(crate) fn run() -> Result<(usize, usize)> {
-    let data = utils::read_i64s("data/day01.txt")?;
+    let data = read_data::<usize>("data/day01.txt")?;
     Ok((
         count_incrementing_windows(1, &data),
         count_incrementing_windows(3, &data),
@@ -19,14 +19,14 @@ mod tests {
 
     #[test]
     fn test_example() {
-        let data = utils::read_i64s("data/day01-test.txt").unwrap();
+        let data = read_data::<usize>("data/day01-test.txt").unwrap();
         assert_eq!(count_incrementing_windows(1, &data), 7);
         assert_eq!(count_incrementing_windows(3, &data), 5);
     }
 
     #[test]
     fn test_my_data() {
-        let data = utils::read_i64s("data/day01.txt").unwrap();
+        let data = read_data::<usize>("data/day01.txt").unwrap();
         assert_eq!(count_incrementing_windows(1, &data), 1298);
         assert_eq!(count_incrementing_windows(3, &data), 1248);
     }
diff --git a/src/utils.rs b/src/utils.rs
index 898d2fd..b9a3384 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -1,11 +1,20 @@
 use anyhow::Result;
-use std::fs;
+use std::{fs, str::FromStr};
 
-pub fn read_i64s(filename: &str) -> Result<Vec<i64>> {
-    Ok(read_file(filename)?
-        .lines()
-        .map(|s| s.parse::<i64>().expect("i64 parse error"))
-        .collect())
+pub fn read_data<T: FromStr>(filename: &str) -> Result<Vec<T>> {
+    parse_data(&read_file(filename)?)
+}
+
+pub fn parse_data<T: FromStr>(s: &str) -> Result<Vec<T>> {
+    let mut ret = Vec::new();
+    for l in s.lines() {
+        let data = match l.parse::<T>() {
+            Ok(d) => d,
+            Err(_) => panic!("parse error"),
+        };
+        ret.push(data);
+    }
+    Ok(ret)
 }
 
 pub fn read_file(filename: &str) -> Result<String> {