新手小白求助下，不知道错哪了

随机生成5道10以内的加法题目，错误提示是： error: ‘end1’ was not declared in this scope
具体代码如下

#include<iostream>
#include<ctime>
#include<stdlib.h>
using namespace std;
int main()
{
    srand(time(0));
    cout<<rand()%10<<"+"<<rand()%10<<"="<<end1;
    cout<<rand()%10<<"+"<<rand()%10<<"="<<end1;
    cout<<rand()%10<<"+"<<rand()%10<<"="<<end1;
    cout<<rand()%10<<"+"<<rand()%10<<"="<<end1;
    return 0;
}