peaks() {
    local -n _arr="$1"
    local _n=${#_arr[@]}
    if (( _n <= 2 )); then
        echo 0
        return
    fi
    local -a _sum
    for ((_i = 0; _i < _n; _i++)); do _sum[_i]=0; done
    local _last=-1 _dist=0 _i
    for ((_i = 1; _i + 1 < _n; _i++)); do
        _sum[_i]=${_sum[_i-1]}
        if (( _arr[_i] > _arr[_i-1] && _arr[_i] > _arr[_i+1] )); then
            if (( _i - _last > _dist )); then _dist=$(( _i - _last )); fi
            _last=$_i
            (( _sum[_i]++ ))
        fi
    done
    _sum[_n-1]=${_sum[_n-2]}
    if (( _sum[_n-1] == 0 )); then
        echo 0
        return
    fi
    if (( _n - _last > _dist )); then _dist=$(( _n - _last )); fi
    local _j
    for ((_i = (_dist >> 1) + 1; _i < _dist; _i++)); do
        if (( _n % _i == 0 )); then
            _last=0
            for ((_j = _i; _j <= _n; _j += _i)); do
                if (( _sum[_j-1] <= _last )); then
                    break
                fi
                _last=${_sum[_j-1]}
            done
            if (( _j > _n )); then
                echo $(( _n / _i ))
                return
            fi
        fi
    done
    for ((_last = _dist; _n % _last != 0; )); do
        ((_last++))
    done
    echo $(( _n / _last ))
}