Problems > Triangular Number Modulo

Triangular Number Modulo

Difficulty: 1000 4000 ms 128 MB

math

Print 1 + 2 + … + N modulo 109+7.

Input: one integer N.

Output: N(N+1)/2 mod 109+7.

Constraints:

  • 1 ≤ N ≤ 1018

Sample Tests

Input 1
5
Output 1
15
Input 2
1
Output 2
1

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