diff --git a/packages/hydrojudge/src/cases.ts b/packages/hydrojudge/src/cases.ts
index b9e614eb5..36d707166 100644
--- a/packages/hydrojudge/src/cases.ts
+++ b/packages/hydrojudge/src/cases.ts
@@ -14,11 +14,11 @@ function isValidConfig(config) {
     if (config.count > (getConfig('testcases_max') || 100)) {
         throw new FormatError('Too many testcases. Cancelled.');
     }
-    const time = Math.sum(config.subtasks.map((subtask) => Math.sum(subtask.cases.map((c) => c.time))));
+    const time = Math.sum(...config.subtasks.flatMap((subtask) => subtask.cases.map((c) => c.time)));
     if (time > (getConfig('total_time_limit') || 60) * 1000) {
         throw new FormatError('Total time limit longer than {0}s. Cancelled.', [+getConfig('total_time_limit') || 60]);
     }
-    const memMax = Math.max(config.subtasks.map((subtask) => Math.max(subtask.cases.map((c) => c.memory))));
+    const memMax = Math.max(...config.subtasks.flatMap((subtask) => subtask.cases.map((c) => c.memory)));
     if (memMax > parseMemoryMB(getConfig('memoryMax'))) throw new FormatError('Memory limit larger than memory_max');
     if (!['default', 'strict'].includes(config.checker_type || 'default') && !config.checker) {
         throw new FormatError('You did not specify a checker.');