func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 3e4 + 100, M = 210;   int gi() {     int w = 0;     bool q = 1;     char c = getchar();     while ((c <  0  || c >  9 ) && c !=  - ) c = getchar();     if (c ==  - ) q = 0, c = getchar();     while (c >=  0  && c <=  9 ) w = w * 10 + c -  0 , c = getchar();     return q ? w : -w;   }   void go() {     puts( -1 );     exit(0);   }   int d[M][N], id[N];   int p[M][N], pre[N];   bool in[N];   int C;   int fa[N];   vector<int> e[N];   inline int find(int x) { return fa[x] == x ? x : fa[x] = find(fa[x]); }   vector<pair<int, int> > sub[N];   inline void link(int a, int b) {     if (find(a) == find(b)) go();     fa[find(a)] = find(b);     e[a].push_back(b);     e[b].push_back(a);   }   inline void dfs(int k, int D, int fa) {     if (D != d[C][k]) go();     for (int t : e[k])       if (t != fa) dfs(t, D + 1, k);   }   int main() {     int n = gi(), m = gi(), i, j, k, last, ld, t, mx, to;     for (i = 1; i <= n; i++) fa[i] = i;     for (i = 1; i <= m; i++) {       for (j = 1; j <= n; j++)         if (!(d[i][j] = gi())) id[i] = j;       if (!id[i]) go();     }     p[1][0] = id[1];     in[id[1]] = true;     for (k = 2; k <= m; k++) {       for (i = 1; i <= n; i++)         if (d[1][i] + d[k][i] == d[1][id[k]]) p[k][d[1][i]] = i, in[i] = true;       for (i = d[1][id[k]]; i; i--) {         if (!p[k][i]) go();         pre[p[k][i]] = p[k][i - 1];       }     }     for (k = 1; k <= n; k++)       if (!in[k]) {         mx = -1;         for (i = 1; i <= m; i++) {           t = (d[1][id[i]] + d[1][k] - d[i][k]) / 2;           if (t > mx) mx = t, to = p[i][t];         }         sub[to].push_back(make_pair(d[1][k], k));       }     for (k = 1; k <= n; k++) {       sort(sub[k].begin(), sub[k].end());       for (i = 0, last = k, ld = d[1][k]; i < sub[k].size(); i++) {         if (i && sub[k][i].first != sub[k][i - 1].first)           ld = d[1][last = sub[k][i - 1].second];         if (sub[k][i].first != ld + 1) go();         pre[sub[k][i].second] = last;       }     }     for (i = 1; i <= n; i++)       if (pre[i])         link(pre[i], i);       else if (i != id[1])         go();     for (i = 1; i <= n; i++)       if (pre[i]) printf( %d %d n , pre[i], i);     return 0;   }   