import Foundation

private func readInt() -> [Int]{
    return readLine()!.split(separator: " ").map{Int($0)!}
}

func mainA() {
    let line = readInt()
    let S = line[0]
    let W = line[1]
    
    if W >= S {
        print("unsafe")
    } else {
        print("safe")
    }
    

}

mainA()
