#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
void *wmem;
char memarr[96000000];
template<class S, class T> inline S max_L(S a,T b){
  return a>=b?a:b;
}
template<class T> inline void walloc1d(T **arr, int x, void **mem = &wmem){
  static int skip[16] = {0, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
  (*mem) = (void*)( ((char*)(*mem)) + skip[((unsigned long long)(*mem)) & 15] );
  (*arr)=(T*)(*mem);
  (*mem)=((*arr)+x);
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
inline void rd(char &c){
  int i;
  for(;;){
    i = getchar_unlocked();
    if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF){
      break;
    }
  }
  c = i;
}
inline int rd(char c[]){
  int i;
  int sz = 0;
  for(;;){
    i = getchar_unlocked();
    if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF){
      break;
    }
  }
  c[sz++] = i;
  for(;;){
    i = getchar_unlocked();
    if(i==' '||i=='\n'||i=='\r'||i=='\t'||i==EOF){
      break;
    }
    c[sz++] = i;
  }
  c[sz]='\0';
  return sz;
}
inline void wt_L(char a){
  putchar_unlocked(a);
}
inline void wt_L(int x){
  int s=0;
  int m=0;
  char f[10];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    putchar_unlocked('-');
  }
  while(s--){
    putchar_unlocked(f[s]+'0');
  }
}
template<class S> void arrInsert(const int k, int &sz, S a[], const S aval){
  int i;
  sz++;
  for(i=sz-1;i>k;i--){
    a[i] = a[i-1];
  }
  a[k] = aval;
}
template<class S, class T> void arrInsert(const int k, int &sz, S a[], const S aval, T b[], const T bval){
  int i;
  sz++;
  for(i=sz-1;i>k;i--){
    a[i] = a[i-1];
  }
  for(i=sz-1;i>k;i--){
    b[i] = b[i-1];
  }
  a[k] = aval;
  b[k] = bval;
}
template<class S, class T, class U> void arrInsert(const int k, int &sz, S a[], const S aval, T b[], const T bval, U c[], const U cval){
  int i;
  sz++;
  for(i=sz-1;i>k;i--){
    a[i] = a[i-1];
  }
  for(i=sz-1;i>k;i--){
    b[i] = b[i-1];
  }
  for(i=sz-1;i>k;i--){
    c[i] = c[i-1];
  }
  a[k] = aval;
  b[k] = bval;
  c[k] = cval;
}
template<class S, class T> inline S chmax(S &a, T b){
  if(a<b){
    a=b;
  }
  return a;
}
struct graph{
  int N;
  int *es;
  int **edge;
  void setEdge(int N__, int M, int A[], int B[], void **mem = &wmem){
    int i;
    N = N__;
    walloc1d(&es, N, mem);
    walloc1d(&edge, N, mem);
    for(i=(0);i<(N);i++){
      es[i] = 0;
    }
    for(i=(0);i<(M);i++){
      es[A[i]]++;
      es[B[i]]++;
    }
    for(i=(0);i<(N);i++){
      walloc1d(&edge[i], es[i], mem);
    }
    for(i=(0);i<(N);i++){
      es[i] = 0;
    }
    for(i=(0);i<(M);i++){
      edge[A[i]][es[A[i]]++] = B[i];
      edge[B[i]][es[B[i]]++] = A[i];
    }
  }
  void getDist(int root, int res[], void *mem = wmem){
    int i;
    int j;
    int k;
    int*q;
    int s;
    int z;
    walloc1d(&q, N, &mem);
    for(i=(0);i<(N);i++){
      res[i]=-1;
    }
    res[root]=0;
    s=0;
    z=1;
    q[0]=root;
    while(z){
      i=q[s++];
      z--;
      for(j=(0);j<(es[i]);j++){
        k=edge[i][j];
        if(res[k]>=0){
          continue;
        }
        res[k]=res[i]+1;
        q[s+z++]=k;
      }
    }
  }
  int bipartite(int res[] = NULL, void *mem = wmem){
    int i;
    int j;
    int k;
    int *st;
    int sts;
    if(res==NULL){
      walloc1d(&res, N, &mem);
    }
    walloc1d(&st, N, &mem);
    for(i=(0);i<(N);i++){
      res[i] = -1;
    }
    for(i=(0);i<(N);i++){
      if(res[i]==-1){
        res[i] = 0;
        sts = 0;
        st[sts++] = i;
        while(sts){
          i = st[--sts];
          for(j=(0);j<(es[i]);j++){
            k = edge[i][j];
            if(res[k]==-1){
              res[k] = 1 - res[i];
              st[sts++] = k;
            }
            if(res[i] + res[k] != 1){
              return 0;
            }
          }
        }
      }
    }
    return 1;
  }
}
;
int N;
int M;
int A[100000];
int B[100000];
int dist[200];
int mx;
char S[200][202];
int main(){
  int i;
  wmem = memarr;
  int k;
  graph g;
  rd(N);
  {
    int Lj4PdHRW;
    for(Lj4PdHRW=(0);Lj4PdHRW<(N);Lj4PdHRW++){
      rd(S[Lj4PdHRW]);
    }
  }
  for(i=(0);i<(N);i++){
    int j;
    for(j=(i+1);j<(N);j++){
      if(S[i][j]=='1'){
        arrInsert(M,M,A,i,B,j);
      }
    }
  }
  g.setEdge(N,M,A,B);
  if(g.bipartite()==0){
    wt_L(-1);
    wt_L('\n');
    return 0;
  }
  for(i=(0);i<(N);i++){
    g.getDist(i, dist);
    {
      int KL2GvlyY;
      int Q5VJL1cS;
      if(N==0){
        Q5VJL1cS = 0;
      }
      else{
        Q5VJL1cS = dist[0];
        for(KL2GvlyY=(1);KL2GvlyY<(N);KL2GvlyY++){
          Q5VJL1cS = max_L(Q5VJL1cS, dist[KL2GvlyY]);
        }
      }
      k =Q5VJL1cS;
    }
    {
      int e98WHCEY;
      int cTE1_r3A;
      if(N==0){
        cTE1_r3A = 0;
      }
      else{
        cTE1_r3A = dist[0];
        for(e98WHCEY=(1);e98WHCEY<(N);e98WHCEY++){
          cTE1_r3A = max_L(cTE1_r3A, dist[e98WHCEY]);
        }
      }
      chmax(mx, cTE1_r3A);
    }
  }
  wt_L(mx + 1);
  wt_L('\n');
  return 0;
}
// cLay varsion 20190929-1

// --- original code ---
// int N, M, A[1d5], B[1d5];
// int dist[200], mx;
// char S[200][202];
// {
//   int k;
//   graph g;
//   rd(N,S(N));
//   rep(i,N) rep(j,i+1,N) if(S[i][j]=='1') arrInsert(M,M,A,i,B,j);
//   g.setEdge(N,M,A,B);
//   if(g.bipartite()==0) wt(-1), return 0;
//   rep(i,N){
//     g.getDist(i, dist);
//     k = max(dist(N));
//     mx >?= max(dist(N));
//   }
//   wt(mx + 1);
// }


Measured memory_bytes: 640