Bessie has invented a new programming language, but since there is no compiler yet, she needs your help to actually run her programs.

COWBASIC is a simple, elegant language. It has two key features: addition and MOO loops. Bessie has devised a clever solution to overflow: all addition is done modulo 10^9+7. But Bessie's real achievement is the MOO loop, which runs a block of code a fixed number of times. MOO loops and addition can, of course, be nested.

Given a COWBASIC program, please help Bessie determine what number it returns.

Scoring

In 20 percent of all test cases - MOO loops are not nested.
In another 20 percent of all test cases - The program only has 1 variable. MOO loops can be nested.
In the remaining test cases, there are no further restrictions.

Problem credits: Jonathan Paulson

#4024 upload - done - how_to_reg -

COWBASIC timer 2s memory 512MB

#4024

COWBASIC 2s 512MB