diff --git a/020/main.rs b/020/main.rs
new file mode 100644
index 0000000..cd758ac
--- /dev/null
+++ b/020/main.rs
@@ -0,0 +1,66 @@
+struct Num { rdigits: Vec<u8> }
+
+impl Num {
+    pub fn from(s: &String) -> Num {
+        let rd: Vec<u8> = s.chars().rev()
+                    .map(|c| String::from(c).parse::<u8>().unwrap())
+                    .collect();
+        Num { rdigits: rd }
+    }
+    pub fn add(&self, n: &Num) -> Num {
+        let mut xs = self.rdigits.clone();
+        let mut ys = n.rdigits.clone();
+        let mut rs: Vec<u8> = Vec::new();
+
+        while xs.len() < ys.len() { xs.push(0); }
+        while ys.len() < xs.len() { ys.push(0); }
+
+        let mut rm = 0u8;
+        for (a, b) in xs.iter().zip(ys.iter()) {
+            if a + b + rm > 9 {
+                rs.push((a + b + rm) - 10);
+                rm = 1u8;
+            } else {
+                rs.push(a + b + rm);
+                rm = 0u8;
+            }
+        }
+        if rm > 0 { rs.push(1u8); }
+
+        Num { rdigits: rs }
+    }
+    pub fn clone(&self) -> Num {
+        Num { rdigits: self.rdigits.clone() }
+    }
+    pub fn print(&self) {
+        for c in self.rdigits.iter().rev() { print!("{}", c); };
+        println!("");
+    }
+    pub fn sum(&self) -> u32 {
+        let mut res = 0u32;
+        for c in self.rdigits.iter() { res += *c as u32; }
+        res
+    }
+    pub fn mult(&self, n: u32) -> Num {
+        let dd = self.clone();
+        let mut res = Num::from(&String::from("0"));
+        for i in 1..=n {
+            res = res.add(&dd);
+        }
+        res
+    }
+}
+
+
+fn main() {
+    let mut n = Num::from(&String::from("1"));
+    for i in 1..100 {
+        n = n.mult(i);
+    }
+    //let m = n.mult(3);
+
+    n.print();
+    //println!("-----------");
+    println!("[{}]", n.sum());
+
+}