#include<stdio.h>

#define N 100
#define W 10001

int memo[N][W], w[N], wn;

int f(int i, int j)
{
    int k;
    
    if(j == 0 || wn <= i){
        return(j);
    }
    if(0 < memo[i][j]){
        return(memo[i][j]);
    }else{
        memo[i][j] = 1;
        for(k = i; k < wn; k++){
            if(w[k] <= j){
                if(f(i + 1, j - w[k]) == 0){
                    return(0);
                }
            }
        }
    }
    return(memo[i][j]);
}


int main(int argc, const char * argv[])
{
    int i, sum = 0;
    
    memset(memo, -1, sizeof(memo));
    scanf("%d", &wn);
    for(i = 0; i < wn; i++){
        scanf("%d", &w[i]);
        sum += w[i];
    }
    printf("sum=%d\n", sum);
    if(sum % 2 == 1){
        printf("impossible\n");
    }else if(f(0, sum/2) == 0){
        printf("possible\n");
    }else{
        printf("impossible\n");
    }
    return 0;
}