import Foundation

#if swift(>=4.0)
extension String {
    func split(by separator: String) -> [String] {
        return self.components(separatedBy: separator)
    }
    func toArray() -> [String] {
        return self.map{String($0)}
    }
}
#else
extension String {
    func split(by separator: String) -> [String] {
        return self.componentsSeparatedByString(separator)
    }
    var count: Int {
        return self.characters.count
    }
    func toArray() -> [String] {
        return self.characters.map{String($0)}
    }
    func uppercased() -> String {
        return self.uppercaseString
    }
    func lowercased() -> String {
        return self.lowercaseString
    }
}
//extension Array where Element == String {
//    func joined(separator separator: String) -> String {
//        return self.joinWithSeparator(separator)
//    }
//}
extension Array where Element: Comparable {
    func max() -> Element {
        return self.maxElement()!
    }
    func min() -> Element {
        return self.minElement()!
    }
    func sorted() -> Array {
        return self.sort()
    }
    func reversed() -> Array {
        return self.reverse()
    }
    mutating func sort() {
        self.sortInPlace()
    }
}
extension Array {
    init(repeating: Element, count: Int) {
        self.init(count: count, repeatedValue: repeating)
    }
}
func stride<T: Strideable>(from start: T, to end: T, by stride: T.Stride) -> StrideTo<T> {
    return start.stride(to: end, by: stride)
}
#endif
func readInt() -> Int? {
    return Int(readLine()!)
}
func readStringSplit(by separator: String) -> [String] {
    return readLine()!.split(by: separator)
}
func readIntSplit(by separator: String) -> [Int] {
    return readLine()!.split(by: separator).map{Int($0)!}
}
func exponentiate(_ lhs: Int, _ rhs: Int) -> Int {
    return (0..<rhs).reduce(1){i,_ in i*lhs}
}

/*************** テストスペース ***************/

//let input = readIntSplit(by: " ")
//let (N, M, X) = (input[0], input[1], input[2])
//let A = readIntSplit(by: " ")

/*************** メインプログラム ***************/

let N = readInt()!
let S = readLine()!.toArray()
var ans1 = 0
var ans2 = 0
var flag1 = false
var flag2 = true
for i in 0..<N {
    if S[i] == "#" {
        if flag2 {
            ans1 += 1
        }
        flag1 = true
    } else {
        if flag1 {
            ans2 += 1
        }
        flag2 = false
    }
}
print(min(ans1, ans2))
