AC043 in rust, finished all. (D doesn't get tested correctly locally)

atcoder/beginner_contests/abc043/src/bin/a.rs

@@ -0,0 +1,11 @@
+use proconio::input;
+
+fn main() {
+    input!{
+        n: u32,
+    };
+
+    let result = n * (n + 1) / 2;
+
+    println!("{}", {result});
+}