>>686
for(i=0;i<N;i++) {
if(map[0][i] == 'b')
map[0][i] = 'c';
if(map[N-1][i] == 'b')
map[N-1][i] = 'c';
if(map[i][0] == 'b')
map[i][0] = 'c';
if(map[i][N-1] == 'b')
map[i][N-1] = 'c';
}

while(1) {
int f = 1;
for(i=1;i<N-1;i++) {
for(j=1;j<N-1;j++) {
if(map[i][j] == 'b') {
int k;
int di[4] = {-1, 0, 0, 1};
int dj[4] = {0, -1, 1, 0};
for(k=0;k<4;k++) {
if(map[i+di[k]][j+dj[k]] == 'c') {
map[i][j] = 'c';
f = 0;
}
}
}
}
}
if(f)
break;
}