diff --git a/test.c b/test.c
index 6b61525..7fe27b8 100644
--- a/test.c
+++ b/test.c
@@ -5,11 +5,7 @@
 
 int sum(int n)
 {
-    int sum = 0;
-    for(int i = 1; i <= n; i++) {
-        sum += i;
-    }
-    return sum;
+    return (n * (n - 1)) / 2;
 }
 
 void usage(const char* app_name, const char* err_string)