func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long UNDEF = -1;   const long long INF = 1e18;   template <typename T>   inline bool chkmax(T &aa, T bb) {     return aa < bb ? aa = bb, true : false;   }   template <typename T>   inline bool chkmin(T &aa, T bb) {     return aa > bb ? aa = bb, true : false;   }   static char stdinBuffer[1024];   static char *stdinDataEnd = stdinBuffer + sizeof(stdinBuffer);   static const char *stdinPos = stdinDataEnd;   void readAhead(size_t amount) {     size_t remaining = stdinDataEnd - stdinPos;     if (remaining < amount) {       memmove(stdinBuffer, stdinPos, remaining);       size_t sz = fread(stdinBuffer + remaining, 1,                         sizeof(stdinBuffer) - remaining, stdin);       stdinPos = stdinBuffer;       stdinDataEnd = stdinBuffer + remaining + sz;       if (stdinDataEnd != stdinBuffer + sizeof(stdinBuffer)) *stdinDataEnd = 0;     }   }   int readInt() {     readAhead(16);     int x = 0;     bool neg = false;     while (*stdinPos ==     || *stdinPos ==   n ) ++stdinPos;     if (*stdinPos ==  - ) {       ++stdinPos;       neg = true;     }     while (*stdinPos >=  0  && *stdinPos <=  9 ) {       x *= 10;       x += *stdinPos -  0 ;       ++stdinPos;     }     return neg ? -x : x;   }   char readCh() {     readAhead(16);     while (*stdinPos ==     || *stdinPos ==   n ) ++stdinPos;     char ans = *stdinPos;     ++stdinPos;     return ans;   }   inline int rri() {     char c;     while (c = getchar(), c <=    )       ;     bool sign = c ==  - ;     if (sign) {       c = getchar();     }     int res = c -  0 ;     while (c = getchar(), c >=  0  && c <=  9 ) {       res = res * 10 + (c -  0 );     }     return sign ? -res : res;   }   inline long long rrl() {     char c;     while (c = getchar(), c <=    )       ;     bool sign = c ==  - ;     if (sign) {       c = getchar();     }     long long res = c -  0 ;     while (c = getchar(), c >=  0  && c <=  9 ) {       res = res * 10 + (c -  0 );     }     return sign ? -res : res;   }   inline char rrc() {     char c;     while (c = getchar(), c <=    )       ;     return c;   }   inline int rrs(char *target) {     char c;     while (c = getchar(), c <=    )       ;     int idx = -1;     target[++idx] = c;     while (1) {       c = getchar();       if (c <=    ) {         target[++idx] =   0 ;         return idx;       }       target[++idx] = c;     }   }   vector<vector<int> > matrixUnit(long long n) {     vector<vector<int> > res(n, vector<int>(n));     for (long long i = 0; i < n; i++) res[i][i] = 1;     return res;   }   vector<vector<int> > matrixMul(const vector<vector<int> > &a,                                  const vector<vector<int> > &b) {     long long n = a.size();     long long m = a[0].size();     long long k = b[0].size();     vector<vector<int> > res(n, vector<int>(k));     for (long long i = 0; i < n; i++)       for (long long j = 0; j < k; j++)         for (long long p = 0; p < m; p++)           res[i][j] = (res[i][j] + (long long)a[i][p] * b[p][j]) % 1000000007LL;     return res;   }   void matrixMult(vector<vector<int> > &res, const vector<vector<int> > &a,                   const vector<vector<int> > &b) {     long long n = a.size();     long long m = a[0].size();     long long k = b[0].size();     for (long long i = 0; i < n; i++)       for (long long j = 0; j < k; j++) {         long long ans = 0;         for (long long p = 0; p < m; p++)           ans = (ans + (long long)a[i][p] * b[p][j]) % 1000000007LL;         res[i][j] = ans;       }   }   const int mn = 2004;   bitset<mn> g[mn];   bool bf(int n) {     vector<vector<int> > inp;     inp.resize(n);     for (int x = 0; x < n; x++) {       inp[x].resize(n);       for (int y = 0; y < n; y++) inp[x][y] = g[x][y];     }     vector<vector<int> > a = inp;     for (int k = 0; k < 500; k++) {       bool ok = 1;       for (int i = 0; i < n; i++)         for (int j = 0; j < n; j++) {           if (a[i][j] == 0) {             ok = 0;             break;           }         }       if (ok) return 1;       a = matrixMul(a, inp);     }     return 0;   }   bitset<mn> h[mn];   bitset<mn> seen;   bool solve2(int n) {     queue<int> q;     for (int x = 0; x < n; x++) {       if (h[0][x]) q.push(x);     }     seen = h[0];     while (!q.empty()) {       int x = q.front();       q.pop();       for (int y = 0; y < n; y++) {         if ((!seen[y]) && h[x][y]) {           q.push(y);           seen[y] = true;         }       }     }     assert(seen.count() <= n);     return (int)seen.count() == n;   }   bool solve(int n) {     int spec = -1;     for (int k = 0; k < n; k++)       if (g[k][k]) spec = k;     assert(spec != -1);     for (int x = 0; x < n; x++)       for (int y = 0; y < n; y++) {         int sx = (x == spec || x == 0) ? x ^ spec : x;         int sy = (y == spec || y == 0) ? y ^ spec : y;         h[sx][sy] = g[x][y];       }     assert(h[0][0]);     if (!solve2(n)) return 0;     for (int x = 0; x < n; x++)       for (int y = 0; y < n; y++) {         g[x][y] = h[y][x];       }     for (int x = 0; x < n; x++) h[x] = g[x];     if (!solve2(n)) return 0;     return 1;   }   void test() {     srand(time(0) + clock() + rand());     for (int j = 0; j < 1000; j++) {       int n = (rand() % 6) + 1;       for (int x = 0; x < n; x++) {         h[x].reset();         g[x].reset();         for (int y = 0; y < n; y++) g[x][y] = rand() & 1;       }       int k = rand() % n;       g[k][k] = 1;       bool b = bf(n);       bool s = solve(n);       if (b != s) {         for (int x = 0; x < n; x++) {           for (int y = 0; y < n; y++) printf( %d , (int)g[x][y]);           printf(  n );         }         printf( b:%d s:%d n , b, s);       }     }   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     int n = readInt();     for (int x = 0; x < n; x++)       for (int y = 0; y < n; y++) {         int t = readInt();         t = (t > 0) ? 1 : 0;         g[x][y] = t;       }     bool final = solve(n);     if (final)       printf( YES n );     else       printf( NO n );   }   