Task #M001A

Memory 16 MB Time 1000 ms Complexity 15 %

Variant

Akrom matematika fani bo’yicha tuzilgan savolni qiymatlarini o’zgartirgan holatda yangi variant hosil qilmoqchi. Akromning matematik masalasida n ta qiymat mavjud bo’lib bu qiymatlarning har biri [L_i, R_i] orasidagi butun son bo'lishi mumkin. Lekin Akrom nol sonini yoqtirmaganligi uchun qiymatlarning birortasi ham nolga teng bo’lishi mumkin emas.

Akrom endi o’ylab qoldi u ushbu masalaning necha xil variantini hosil qila oladi?

Input:

Kirish faylining dastlabki satrida bitta butun son, n (1 ≤ n ≤ 100) soni, keyingi n ta qatorda 2 tadan butun son, L_i va R_i(-10 000 ≤ L_i ≤ R_i≤10 000)

Output:

Chiqish faylida yagona butun son, variantlar sonini chop eting. Bu son juda katta bo’lishi mumkin, shuning uchun siz bu sonning 10⁹+7 ga bo’lgandagi qoldig’ini chiqaring.

Examples

#	input.txt	output.txt
1	1 2 5	4
2	3 2 5 1 6 -1 4	120

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