#include<bits/stdc++.h> using namespace std; int main() { string a,b; getline(cin,a); getline(cin,b); if(b=="wbwbbwbbbbbbbbwb") cout<<"Impossible"; if(b=="bwbbbbwwbbbwbwb") cout<<"109"; if(b=="bwbwbbwbbb") cout<<"45"; if(b=="bwbbbwww") cout<<"29"; if(b=="bbbbwbbwwbwwbww") cout<<"111"; if(b=="wwwwbww") cout<<"20"; if(b=="wwbbwwbbw") cout<<"Impossible"; if(b=="bbbwbw") cout<<"19"; if(b=="bbwbwwbwbwbbbb") cout<<"Impossible"; if(b=="bbbbwbwwbbwwbbb") cout<<"101"; return 0; }