diff --git a/README.md b/README.md
index 6da029a..a9f8427 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,174 @@
 # a
 
+一、调和级数
+
+#include<stdio.h>
+#include<math.h>
+
+int main(){
+    int n,i;
+    scanf("%d", &n); 
+    double p=0;
+    /***********BEGIN***********/
+for (i=1;i<=n;i++)
+p=p+pow(-1,(i+1))*1.0/i;
+    /***********END***********/
+    printf("%.2f",p);
+    return 0;
+}
+二、计算n的阶乘
+#include<stdio.h>
+int main(){
+    /*****************BEGIN*****************/
+int n,s=1,i;
+scanf("%d",&n);
+for(i=1;i<=n;i++)
+s=s*i;
+printf("%d",s);
+
+    /******************END******************/
+    return 0;
+}
+三、最大的数
+#include<stdio.h>
+
+int main(){
+    int arr[100],n,i;
+    scanf("%d", &n);
+    for(i=0;i<n;i++) scanf("%d", &arr[i]);
+    /*****************BEGIN*****************/
+int max=0;
+for (i=0;i<n;i++)
+{if(arr[i]>arr[max])
+max=i;
+}
+printf("%d",max+1);
+
+
+    /******************END******************/
+    return 0;
+}
+四、按照从大到小顺序输出整数
+#include<stdio.h>
+int main(){
+    int a,b;
+    scanf("%d %d", &a, &b);
+    /*****************BEGIN*****************/
+if(a>b)
+printf("%d %d",a,b);
+else printf("%d %d",b,a);
+    
+    /******************END******************/
+    return 0;
+}
+五、数组排序
+#include <stdio.h>
+void sort(int arr[]){
+    /*****************BEGIN*****************/
+int t,i,j;
+for(i=0;i<20;i++)
+  for (j=0;j<19-i;j++)
+  {if (arr[j]>arr[j+1]){
+      t=arr[j];
+      arr[j]=arr[j+1];
+      arr[j+1]=t;
+  }
+
+  }
+
+    /******************END******************/
+}
+int main(){
+    int x[20], i;
+    for (i = 0; i < 20; i++) scanf("%d", &x[i]);
+    sort(x);
+    for (i = 0; i < 20; i++) printf("%d ", x[i]);
+    return 0;
+}
+
+六、最大公约数和最小公倍数
+#include <stdio.h>
+int main(){
+    int a, b;
+    scanf("%d %d",&a,&b);
+    //*******************BEGIN*******************
+int x,y,z,c;
+x=a;y=b;
+while(b!=0){
+    c=a%b;
+    a=b;
+    b=c;
+}
+z=x*y/a;
+printf("%d %d",a,z);
+
+    //********************END********************
+    return 0;
+}
+
+七、所有偶数平均值
+#include<stdio.h>
+int main(){
+    int M, N;
+    scanf("%d %d", &M, &N);
+    /*****************BEGIN*****************/
+int i=0,n=0;
+float ave,sum;
+for(i=M;i<=N;i++){
+  if(i%2==0){
+      sum=sum+i;
+      n++;
+  }}
+ave=sum/n;
+printf("%.2f",ave);
+
+    /******************END******************/
+    return 0;
+}
+八、寻找完数
+#include<stdio.h>
+#include<math.h>
+int main(){
+    /*****************BEGIN*****************/
+int num,s,m,i;
+for (num=2;num<=10000;num++){
+s=0;m=0;
+for(i=1;i<num;i++)
+    if((num%i)==0)
+s=s+i;
+if(s==num)
+{printf("%d [",num);
+for(i=1;i<num;i++)
+{if (num%i==0)
+{printf("%d",i);
+m=m+i;
+if(m!=num)
+printf("+");}}
+printf("]");
+printf("\n");
+}
+
+}
+
+    /******************END******************/
+    return 0;
+}
+九、逆序一个数
+#include<stdio.h>
+int main(){
+    int n;
+    scanf("%d", &n);
+    /*****************BEGIN*****************/
+do
+    {
+        printf("%d",n%10);   
+        n = n/10;               
+    }
+    while(n!=0);    
+
+    /******************END******************/
+    return 0;
+}
+
+
+