58 lines
1.0 KiB
Swift
58 lines
1.0 KiB
Swift
let Mod = 1000000007
|
|
|
|
func power(base a: Int, exponent b: Int) -> Int {
|
|
if b == 0 {
|
|
return 1
|
|
}
|
|
|
|
if b == 1 {
|
|
return a
|
|
}
|
|
|
|
var half = power(base: a, exponent: b/2)
|
|
half = (half * half) % Mod
|
|
|
|
if b%2 == 1 {
|
|
return (a * half) % Mod
|
|
}
|
|
else {
|
|
return half
|
|
}
|
|
}
|
|
|
|
func gcd(_ x: Int, _ y: Int) -> Int {
|
|
var a = max(x,y)
|
|
var b = min(x,y)
|
|
|
|
while b != 0 {
|
|
let r = a%b
|
|
a = b
|
|
b = r
|
|
}
|
|
|
|
return a
|
|
}
|
|
|
|
if let M = Int(readLine() ?? "") {
|
|
var result = 0
|
|
|
|
for _ in 0..<M {
|
|
if let input = readLine(),
|
|
let info = input.split(separator: " ").compactMap({Int($0)}) as? [Int],
|
|
info.count == 2
|
|
{
|
|
var N = info[0]
|
|
var S = info[1]
|
|
|
|
let GCD = gcd(N, S)
|
|
N /= GCD
|
|
S /= GCD
|
|
|
|
result += S*(power(base: N, exponent: Mod-2))%Mod
|
|
result %= Mod
|
|
}
|
|
}
|
|
|
|
print(result)
|
|
}
|