1 #define _CRT_SECURE_NO_WARNINGS
2 #include <stdio.h>
3 #include <math.h>
4 #include <algorithm>
5 #include <stdlib.h>
6 #include <vector>
7 #include <map>
8 #include <queue>
9 #include <string>
10 #include <iostream>
11 #include <ctype.h>
12 #include <string.h>
13 #include <set>
14 #include <stack>
15 #include<functional>
16 using namespace std;
17 #define Size 18
18 #define maxn 1<<30
19 #define minn 1e-6
20 int n;
21 int a[Size][Size];
22 int press[Size][Size];
23 int ans=maxn;
24 int isFini = 0;
25 bool guest(){
26 int steps = 0;
27 for (int i = 1; i <= n; i++){
28 if (press[1][i]) steps++;
29 }
30 if (steps == n) isFini = 1;
31 for (int i = 1; i <n; i++)
32 for (int j = 1; j <= n; j++){
33 press[i + 1][j] = (press[i][j] + a[i][j] + press[i - 1][j] + press[i][j - 1] + press[i][j + 1])%2;
34 }
35 for (int i = 1; i <= n; i++){
36 if (a[n][i] != (press[n][i] + press[n-1][i] + press[n][i - 1] + press[n][i + 1])%2) return false;
37 }
38 steps = 0;
39 for (int i = 1; i <= n; i++)
40 for (int j = 1; j <= n; j++){
41 if (press[i][j]) steps++;
42 }
43 if (steps < ans) ans = steps;
44 return false;
45 }
46 void solve(){
47 int c = 1;
48 while (guest()==false){
49 if (isFini) break;
50 press[1][1]++;
51 c = 1;
52 while (press[1][c] > 1){
53 press[1][c] = 0;
54 c++;
55 press[1][c]++;
56 }
57 }
58 if (ans == maxn) cout << "inf" << endl;
59 else cout << ans << endl;
60 }
61 int main(){
62 cin >> n;
63 for (int i = 1; i <= n; i++)
64 for (int j = 1; j <= n; j++){
65 char c;
66 cin >> c;
67 a[i][j] = c == 'w' ? 1 : 0;
68 }
69 solve();
70 system("pause");
71 }
