c++开始

int x;

int y;

int sum;

int value;

int main()

{

std::cout << "hello world" << std::endl;

std::cin >> x;

while (y <= x)

{

sum +=  y;

y++;

}

std::cout << "sum:" << sum << std::endl;

sum = 0;

std::cout << "循环输入:" << std::endl;

while (std::cin >> value){

//输入ctrl+z+enter结束

if (value <0)break;

sum += value;

}

std::cout << "sum:" << sum << std::endl;

getchar();

system("pause");//暂停

return 0;

}