#include<bits/stdc++.h>
#define poly vector<int>
#define IOS ios::sync_with_stdio(false)
#define ll __int128
#define mp make_pair
#define mt make_tuple
#define pa pair < int,int >
#define fi first
#define se second
#define inf 1e18
#define mod 998244353
#define sz(x) ((int)((x).size()))
#define int ll
// #define N 
using namespace std;
inline char gc(){static char buf[100000],*p1=buf,*p2=buf;return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;}
#define gc getchar
inline ll read(){char c=gc();ll su=0,f=1;for (;c<'0'||c>'9';c=gc()) if (c=='-') f=-1;for (;c>='0'&&c<='9';c=gc()) su=su*10+c-'0';return su*f;}
inline void write(ll x){if (x<0){putchar('-');write(-x);return;}if (x>=10) write(x/10);putchar(x%10+'0');}
inline void writesp(ll x){write(x),putchar(' ');}
inline void writeln(ll x){write(x);putchar('\n');}
void BellaKira()
{
    string st;
    cin>>st;
    for (int i=0;i+1<st.size();i++)
        if (st[i]=='O'&&st[i+1]=='O')
        {
            puts("INVALID\n");
            return;
        }
    if (st.back()=='E')
    {
        puts("INVALID\n");
        return;
    }
    for (int s=2;s;s*=2)
    {
        int x=s;
        bool bl=1;
        for (int i=sz(st)-1;i>=0;i--)
        {
            if (st[i]=='O')
            {
                if ((x-1)%3!=0)
                {
                    bl=0;
                    break;
                }
                x=(x-1)/3;
                if (x%2==0||x==1) 
                {
                    bl=0;
                    break;
                }
            } else x=x*2;
        }
        if (bl)
        {
            writeln(x);
            return;
        }
    }


}
signed main()
{
    int T=1;
    while (T--)
    {
        BellaKira();
    }
}
/*list:
1.mod 998244353 or 1e9+7 or ???
2.N
3.duipai shuju xingtai duoyidian
...
*/