func Solution(A []int) int {
    // write your code in Go 1.4
    
    
    var pom = make([]int, len(A)+1)
    pom[0] = 0;
    for _, v := range A {
        if v > 0 && v <= len(A) {
            pom[v-1] = 1
        }
    }
    
    //fmt.Println(pom)
    
    for i, v := range pom {
        if v == 0 {
            return i+1
        }
    }
    
    return 1
}