Sum 1..N
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Contribute a translation- Time limit
- 1000 ms
- Memory limit
- 256 MB
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Statement
Given $N$, print the sum $1 + 2 + \dots + N$.
Input
One integer $N$ ($1 \le N \le 10^9$).
Output
Print the sum. Use 64-bit arithmetic.
Examples
Sample input 1
3
Sample output 1
6
Notes
Subtask 1 (40 pts): $N \le 1000$. Subtask 2 (60 pts): $N \le 10^9$.
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