diff --git a/packages/hydrooj/src/lib/content.ts b/packages/hydrooj/src/lib/content.ts
index f09d94b95..3337be70d 100644
--- a/packages/hydrooj/src/lib/content.ts
+++ b/packages/hydrooj/src/lib/content.ts
@@ -15,15 +15,15 @@ export function buildContent(source: ProblemSource, type: 'markdown' | 'html' =
     // required by upgrade 90_91
     if (source instanceof Array) {
         return type === 'html'
-            ? source.map((node) => [
+            ? source.flatMap((node) => [
                 node.type !== 'Plain' ? `<h2>${node.sectionTitle}</h2>` : '',
                 node.type === 'Sample'
                     ? `<pre><code class="language-input${++cnt}">${node.payload[0]}</code></pre>`
                     + `<pre><code class="language-output${cnt}">${node.payload[1]}</code></pre>`
                     : '',
                 node.text,
-            ].join('\n')).join('\n')
-            : source.map((node) => [
+            ]).join('\n')
+            : source.flatMap((node) => [
                 node.type !== 'Plain' && (node.type !== 'Sample' || !cnt) ? `## ${node.sectionTitle}` : '',
                 ...node.type === 'Sample'
                     ? [
@@ -41,7 +41,7 @@ export function buildContent(source: ProblemSource, type: 'markdown' | 'html' =
                 '',
                 node.text,
                 '',
-            ].join('\n')).join('\n');
+            ]).join('\n');
     }
     return type === 'html'
         ? [
@@ -60,9 +60,9 @@ export function buildContent(source: ProblemSource, type: 'markdown' | 'html' =
             ...source.source ? [`<h2>${_('Source')}</h2>`, source.source] : [],
         ].join('\n')
         : [
-            ...source.description ? [`## ${_('Description')}`, source.description] : [],
-            ...source.input ? [`## ${_('Input Format')}`, source.input] : [],
-            ...source.output ? [`## ${_('Output Format')}`, source.output] : [],
+            ...source.description ? [`## ${_('Description')}`, '', source.description, ''] : [],
+            ...source.input ? [`## ${_('Input Format')}`, '', source.input, ''] : [],
+            ...source.output ? [`## ${_('Output Format')}`, '', source.output, ''] : [],
             ...(source.samples).map((sample, i) => [
                 `\`\`\`input${i + 1}`,
                 sample[0],
@@ -72,8 +72,8 @@ export function buildContent(source: ProblemSource, type: 'markdown' | 'html' =
                 '```',
             ].join('\n')),
             ...source.samplesRaw ? [source.samplesRaw] : [],
-            ...source.hint ? [`## ${_('Hint')}`, source.hint] : [],
-            ...source.source ? [`## ${_('Source')}`, source.source] : [],
+            ...source.hint ? [`## ${_('Hint')}`, '', source.hint, ''] : [],
+            ...source.source ? [`## ${_('Source')}`, '', source.source, ''] : [],
         ].join('\n');
 }