func solution(_ my_string:String) -> Int {
var arr = my_string.split(separator: " ")
var sepa: [String] = []
var num: [Int] = []
var result = 0
for i in 0..<arr.count{
if i % 2 != 0{
sepa.append(String(arr[i]))
}
else{
if i != 0 && String(arr[i-1]) == "-"{
num.append(Int(String(arr[i]))! * -1)
}
else{
num.append(Int(String(arr[i]))!)
}
}
}
for i in num{
result += i
}
return result
}