#include <bits/stdc++.h>
using namespace std;

#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,b,a) for (int i = (b)-1; i >= (a); i--)
#define ITER(it,a) for (__typeof(a.begin()) it = a.begin(); it != a.end(); it++)
#define FILL(a,value) memset(a, value, sizeof(a))

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;

const double PI = acos(-1.0);
const int INF = 1000 * 1000 * 1000 + 7;
const LL LINF = INF * (LL) INF;

const int MAX = 256;

int DP[MAX][MAX];


int main()
{
    //reopen("in.txt", "r", stdin);
    ios::sync_with_stdio(false); cin.tie(0);

    string s;
    while(getline(cin, s))
    {
        int n = SZ(s);

        FOR (i, 0, n)
        {
            DP[i][i] = 0;
            if (i) DP[i][i-1] = 1;
        }

        FOR (len, 2, n+1)
        {
            FOR (i, 0, n)
            {
                int L = i;
                int R = i + len - 1;
                if (R >= n) break;

                DP[L][R] = false;
                if (s[L] == s[R])
                {
                    if (DP[L+1][R-1])
                    {
                        DP[L][R] = true;
                        continue;
                    }
                }

                FOR (k, L, R)
                {
                    if (DP[L][k] && DP[k+1][R])
                    {
                        DP[L][R] = true;
                        break;
                    }
                }

                if (DP[L][R]) continue;

                if (s[L] == s[R])
                {
                    FOR (k, L+1, R)
                    {
                        if (s[k] == s[L])
                        {
                            if (DP[L+1][k-1] && DP[k+1][R-1])
                            {
                                DP[L][R] = true;
                                break;
                            }
                        }
                    }
                }
            }
        }

        if (DP[0][n-1]) cout<<"solvable\n";
        else cout<<"unsolvable\n";
    }



}