阅读程序，填写对应的输出结果

1. cout << 2 + 1.7 << endl;
   {{ input(1) }}
2. cout << 1 - 0.6 << endl;
   {{ input(2) }}
3. cout << 3 * 2.1 << endl;
   {{ input(3) }}
4. cout << 5 / 2 + 0.5 << endl;
   {{ input(4) }}
5. cout << 2.0 * 5 / 2 << endl;
   {{ input(5) }}
6. cout << 1.0 * 7 / 2 << endl;
   {{ input(6) }}
7. cout << 1e9 - 5e8 << endl; {{ select(7) }}

• 1e8
• 4e8
• 5e8