#include <iostream>
#include <string>
#include <vector>
#include <stack>

int main()
{
    int n = 0;
    std::cin >> n;

    std::stack<int> buf;
    buf.push(0);
    for(int i = 0; i < n; ++i)
    {

        int tmp = 0;
        std::cin >> tmp;

        std::stack<int> tmpbuf;

        while(!buf.empty())
        {
            auto const a = buf.top();
            //std::cout << "a:" << a << std::endl;
            buf.pop();
            tmpbuf.push(tmp + a);
            tmpbuf.push(tmp - a);
        }
        buf = tmpbuf;
    }

    bool found = false;

    while(!buf.empty())
    {
        if( buf.top() == 0 )
            found = true;
        buf.pop();
    }

    if( found )
        std::cout << "possible" << std::endl;
    else
        std::cout << "impossible" << std::endl;

}