/*
Author: QAQAutomaton
Lang: C++
Code: B.cpp
Mail: lk@qaq-am.com
Blog: https://www.qaq-am.com/
*/
#include<bits/stdc++.h>
#define debug(...) fprintf(stderr,__VA_ARGS__)
#define DEBUG printf("Passing [%s] in LINE %d\n",__FUNCTION__,__LINE__)
#define Debug debug("Passing [%s] in LINE %d\n",__FUNCTION__,__LINE__)
#define all(x) x.begin(),x.end()
#define x first
#define y second
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef complex<double> cp;
typedef pair<int,int> pii;
int inf;
const double eps=1e-8;
const double pi=acos(-1.0);
template<class T,class T2>int chkmin(T &a,T2 b){return a>b?a=b,1:0;}
template<class T,class T2>int chkmax(T &a,T2 b){return a<b?a=b,1:0;}
template<class T>T sqr(T a){return a*a;}
template<class T,class T2>T mmin(T a,T2 b){return a<b?a:b;}
template<class T,class T2>T mmax(T a,T2 b){return a>b?a:b;}
template<class T>T aabs(T a){return a<0?-a:a;}
template<class T>int dcmp(T a,T b){return a>b;}
template<int *a>int cmp_a(int x,int y){return a[x]<a[y];}
#define min mmin
#define max mmax
#define abs aabs
struct __INIT__{
	__INIT__(){
		memset(&inf,0x3f,sizeof(inf));
	}
}__INIT___;
namespace io {
	const int SIZE = (1 << 21) + 1;
	char ibuf[SIZE], *iS, *iT, obuf[SIZE], *oS = obuf, *oT = oS + SIZE - 1, c, qu[55]; int f, qr;
	// getchar
	#define gc() (iS == iT ? (iT = (iS = ibuf) + fread (ibuf, 1, SIZE, stdin), (iS == iT ? EOF : *iS ++)) : *iS ++)
	// print the remaining part
	inline void flush () {
		fwrite (obuf, 1, oS - obuf, stdout);
		oS = obuf;
	}
	// putchar
	inline void putc (char x) {
		*oS ++ = x;
		if (oS == oT) flush ();
	}
	template<typename A>
	inline bool read (A &x) {
		for (f = 1, c = gc(); c < '0' || c > '9'; c = gc()) if (c == '-') f = -1;else if(c==EOF)return 0;
		for (x = 0; c <= '9' && c >= '0'; c = gc()) x = x * 10 + (c & 15); x *= f;
		return 1;
	}
	inline bool read (char &x) {
		while((x=gc())==' '||x=='\n' || x=='\r');
		return x!=EOF;
	}
	inline bool read(char *x){
		while((*x=gc())=='\n' || *x==' '||*x=='\r');
		if(*x==EOF)return 0;
		while(!(*x=='\n'||*x==' '||*x=='\r'||*x==EOF))*(++x)=gc();
		*x=0;
		return 1;
	}
	template<typename A,typename ...B>
	inline bool read(A &x,B &...y){
		return read(x)&&read(y...);
	}
	template<typename A>
	inline bool write (A x) {
		if (!x) putc ('0'); if (x < 0) putc ('-'), x = -x;
		while (x) qu[++ qr] = x % 10 + '0',  x /= 10;
		while (qr) putc (qu[qr --]);
		return 0;
	}
	inline bool write (char x) {
		putc(x);
		return 0;
	}
	inline bool write(const char *x){
		while(*x){putc(*x);++x;}
		return 0;
	}
	inline bool write(char *x){
		while(*x){putc(*x);++x;}
		return 0;
	}
	template<typename A,typename ...B>
	inline bool write(A x,B ...y){
		return write(x)||write(y...);
	}
	//no need to call flush at the end manually!
	struct Flusher_ {~Flusher_(){flush();}}io_flusher_;
}
using io :: read;
using io :: putc;
using io :: write;
char s[205][205];
vector<int> to[205];
int col[205];
int n;	
void dfs(int x,int c){
	if(~col[x]){
		if(col[x]!=c)exit(write("-1\n"));
		return;
	}
	col[x]=c;
	for(auto i:to[x])dfs(i,c^1);
}
int q[205],*l,*r;
pii a[205];
int vis[205],inq[205],ans;
void add(pii &a,pii b,int c){
	if(c){++b.y;}
	else --b.x;
	chkmax(a.x,b.x);
	chkmin(a.y,b.y);
}
void solve(int st){
	for(int i=1;i<=n;++i){
		vis[i]=inq[i]=0;	
		a[i]=make_pair(-inf,inf);
	}	
	a[st]=make_pair(0,0);
	inq[*(l=r=q+1)=st]=1;
	for(;l<=r;++l){
		vis[*l]=1;
		for(auto i:to[*l])if(!vis[i]){
			add(a[i],a[*l],col[*l]);
			if(!inq[i])inq[*(++r)=i]=1;
		}
	}
	l=q+1;
	for(;r>=l;--r){
		vis[*r]=0;
		for(auto i:to[*r])if(vis[i])add(a[i],a[*r],col[*r]);
	}
	if(col[st]){
		for(int i=1;i<=n;++i)if(col[i]){
			chkmax(ans,abs(a[i].y*2));
			chkmax(ans,abs(a[i].x*2));
		}else{
			chkmax(ans,abs(a[i].y*2-1));
			chkmax(ans,abs(a[i].x*2-1));
		}
	}
	else{
		for(int i=1;i<=n;++i)if(!col[i]){
			chkmax(ans,abs(a[i].y*2));
			chkmax(ans,abs(a[i].x*2));
		}else{
			chkmax(ans,abs(a[i].y*2+1));
			chkmax(ans,abs(a[i].x*2+1));
		}
	}
}
signed main(){
#ifdef QAQAutoMaton 
	freopen("B.in","r",stdin);
	freopen("B.out","w",stdout);
#endif
	read(n);
	for(int i=1;i<=n;++i){read(s[i]+1);col[i]=-1;}
	for(int i=1;i<=n;++i)for(int j=1;j<=n;++j)if(s[i][j]=='1')to[i].push_back(j);
	dfs(1,0);
	for(int i=1;i<=n;++i)solve(i);
	write(ans+1,'\n');
	return 0;
}



Measured memory_bytes: 2560