#include <cstdio>#include <cstring>#include <algorithm>#include <queue>#include <stack>#include <map>#include <set>#include <climits>#include <iostream>#include <string>using namespace std; #define MP make_pair#define PB push_backtypedef long long LL;typedef unsigned long long ULL;typedef vector<int> VI;typedef pair<int, int> PII;typedef pair<double, double> PDD;const int INF = INT_MAX / 3;const double eps = 1e-8;const LL LINF = 1e17;const double DINF = 1e60;const int maxn = 250;const int dx[] = {0, 0, 1, -1};const int dy[] = {1, -1, 0, 0};int a[maxn][maxn], n;bool fx[maxn];char buf[16][16];void Gauss() {    for(int i = 0; i < n * n; i++) {        int k = i;        while(a[k][i] == 0 && k < n * n) k++;        if(k >= n * n) break;        for(int j = 0; j <= n * n; j++) swap(a[i][j], a[k][j]);        for(int j = 0; j < n * n; j++) if(j != i && a[j][i] != 0) {            for(int k = 0; k <= n * n; k++) {                a[j][k] ^= a[i][k];            }        }    }}void pp() {    for(int i = 0; i < n * n; i++) {        for(int j = 0; j <= n * n; j++) {            printf("%d ", a[i][j]);        }        puts("");    }}int solve() {    memset(a, 0, sizeof(a));    for(int i = 0; i < n; i++) {        for(int j = 0; j < n; j++) {            if(buf[i][j] == ‘w‘) a[i * n + j][n * n] = 1;            else a[i * n + j][n * n] = 0;        }    }    for(int i = 0; i < n; i++) {        for(int j = 0; j < n; j++) {            int u = i * n + j;            a[u][u] = 1;            for(int k = 0; k < 4; k++) {                int nx = i + dx[k], ny = j + dy[k], nu = nx * n + ny;                if(nx >= 0 && nx < n && ny >= 0 && ny < n) {                    a[u][nu] = a[nu][u] = 1;                }            }        }    }    Gauss();    memset(fx, 0, sizeof(fx));    int ans = INF, fcnt = 0;    bool bad = false;    for(int i = 0; i < n * n; i++) {        int nsum = 0;        for(int j = 0; j  < n * n; j++) nsum += a[i][j];        if(nsum == 0 && a[i][n * n] == 1) bad = true;        if(nsum == 0) fx[i] = true, fcnt++;    }    if(bad) return INF;    for(int s = 0; s < (1 << fcnt); s++) {        int nowans = 0;        for(int i = 0; i < n * n - fcnt; i++) {            int col = 0;            for(int j = 0; j < n * n; j++) if(fx[j] && a[i][j]) {                if(s & (1 << (n * n - j - 1))) col ^= 1;            }            if(a[i][n * n] != col) nowans++;         }        int bcnt = 0;        for(int i = 0; i < fcnt; i++) if(s & (1 << i)) bcnt++;        ans = min(nowans + bcnt, ans);    }    return ans;}int main() {    while(scanf("%s%s%s%s", buf[0], buf[1], buf[2], buf[3]) != EOF) {        n = 4;        int ans = solve();        for(int i = 0; i < 4; i++) {            for(int j = 0; j < 4; j++) {                if(buf[i][j] == ‘w‘) buf[i][j] = ‘b‘;                else buf[i][j] = ‘w‘;            }        }        ans = min(ans, solve());        if(ans < INF) printf("%d\n", ans);        else puts("Impossible");    }    return 0;}