import Foundation

let n = Int(readLine()!)!
var tips:[Int] = []
var result = 0

for _ in 0..<n {
    tips.append(Int(readLine()!)!)
}

tips.sort(by: > )

for i in 0..<n{
    let tip = tips[i] - i
    if tip > 0 {
        result += tip
    }
}

print(result)