程序填空题：写出使用格里高利公式求π的近似值的等价程序段

请将程序段B补充完整，使其与程序段A等价。
```
/* 程序段A */
flag = 1;
denominator = 1;
item = 1.0;
pi = 0;
while(fabs(item) >= 0.0001){
item = flag * 1.0 / denominator;
pi = pi + item;
flag = -flag;
denominator = denominator + 2;
}
pi = pi * 4;
```

```c++
/* 程序段B */
flag = 1;
denominator = 1;
item = 1.0;
pi = 0;
while(fabs(item) >= 0.0001){
@@[pi = pi + item;](1)
flag = -flag;
denominator = denominator + 2;
@@[item = flag * 1.0 / denominator; ](1)
}
@@[pi = pi + item;](1)
pi = pi * 4;
```






答案：
第1空：pi = pi + item;

第2空：item = flag * 1.0 / denominator;

第3空：pi = pi + item;