diff --git a/problems/2108/21900398.c b/problems/2108/21900398.c
new file mode 100644
index 0000000..2053f92
--- /dev/null
+++ b/problems/2108/21900398.c
@@ -0,0 +1,65 @@
+#include<stdio.h>
+#include<string.h>
+int main()
+{
+	int n;
+	scanf("%d", &n);
+	int x;
+	char arr[5000];
+	for (x = 0; x < n; x++)
+	{
+		scanf("%d", &arr[x]);
+	}
+	int len=strlen(arr);//길이 구하기 찾기
+	//1. sum구하고
+	int sum = 0;
+	for (x = 0; x < len; x++)
+	{
+		sum += arr[x];
+	}
+	//2. sum/N값 구하기
+	printf("%d\n", sum / n);
+	//3. arr를 sort
+	int a, b;
+	for (a = 0; a < len - 1; a++)
+	{
+		for (b = a + 1; b < len; b++)
+		{
+			if (arr[a] > arr[b])
+			{
+				int temp;
+				temp = arr[a];
+				arr[a] = arr[b];
+				arr[b] = temp;
+
+			}
+		}
+	}
+	//4. arr[N/2+1]출력
+	printf("%d\n", arr[n / 2 ]);
+	//5. count배열만들고
+	int count[200] = { 0 };
+	for (x = 0; x < len; x++)
+	{
+		count[arr[x]]++;
+	}
+	//6. count배열이용해서 최빈값찾기
+	int Max = count[0];
+	int many;
+	for (x = 0; x < len; x++)
+	{
+		if (count[x] > Max)
+		{
+			Max = count[x];
+			many = x;
+		}
+
+	}
+	printf("%d\n", many);
+
+
+	//8. max-min출력
+	printf("%d", arr[len-1] - arr[0]);
+
+
+	return 0;
diff --git a/problems/2581/21900398.c b/problems/2581/21900398.c
new file mode 100644
index 0000000..389bbc2
--- /dev/null
+++ b/problems/2581/21900398.c
@@ -0,0 +1,50 @@
+#include<stdio.h>
+#include<string.h>
+int main()
+{
+	char arr[100] = { 0 };
+	int t = 0;
+	int m, n;
+	scanf("%d\n%d", &m, &n);
+	int i;
+	int a;
+	int flag = 0;
+	for (i = m; i <= n; i++)
+	{
+		for (a = 2; a < i; a++)
+		{
+			if (i%a == 0)
+			{
+				flag = 0;
+				break;
+			}
+			else
+			{
+				flag = 1;
+				
+			}
+		}
+		if (flag == 1)
+		{
+			arr[t] = i;
+			t++;
+		}
+	}
+	int len = strlen(arr);
+	if (len == 0)
+	{
+		printf("-1");
+		return 0;
+	}
+	int sum = 0;
+	int x;
+
+	for (x = 0; x < len; x++)
+	{
+		sum += arr[x];
+	}
+
+	printf("%d %d", sum, arr[0]);
+	return 0;
+
+}