25 lines
485 B
Python
25 lines
485 B
Python
MOD = 1000000007
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def power(x,n) :
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if n==0 :
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return 1
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if n==1 :
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return x%MOD
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half = power(x,n//2)
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result = (half*half)%MOD
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if n%2==1 :
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result = (result*x)%MOD
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return result
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inverse_element_MOD = lambda x: power(x, MOD-2)
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expect_value = lambda a, b : (a*inverse_element_MOD(b))%MOD
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result = 0
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for _ in range(int(input())) :
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S, N = map(int, input().split())
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result = (result + expect_value(N,S))%MOD
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print(result) |