#include <iostream>
#define MAX 999999
using namespace std;

char s[4][4];
int cs[16] = {19,39,78,140,305,626,1252,2248,4880,8992,20032,35968,12544,29184,58368,51200};
int po[16] = {1,2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768};

int main()
{
    int i,j,value = 0;
    int cmin = MAX;
    char c;
    for(i = 0;i < 16;i++)
    {
        cin >> c;
        if(c == 'b')
            value += (int)po[i];
        else    continue;
    }


    for(i = 0;i < 65536;i++)
    {
        int cou = 0;
        int cvalue = value;
        for(j = 0;j < 16;j++)
            if(i & (int)po[j])
            {
                cou++;
                cvalue ^= cs[j];
            }
        if(cvalue == 0 || cvalue == 65535)
            if(cou < cmin)  cmin = cou;
    }
    if(cmin == MAX) cout << "Impossible";
    else cout << cmin << endl;
   return 0;
}