#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    std::vector<int> arr = {1,3,2,4,5,7};

    std::sort(arr.begin(),arr.end());

    for(int i=0; i<arr.size()-1; i++){
            if(arr[i+1]!=arr[i]+1){
                return -1;
            }
    }

    return 0;
}