func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     ;     long long int n;     cin >> n;     vector<vector<long double> > dist(n + 1, vector<long double>(n + 1));     vector<long double> x(n + 1), y(n + 1), z(n + 1);     vector<long long int> vis(n + 1, 0);     for (long long int i = 1; i <= n; i++) cin >> x[i] >> y[i] >> z[i];     for (long long int i = 1; i <= n; i++) {       for (long long int j = 1; j <= n; j++) {         dist[i][j] = (x[i] - x[j]) * (x[i] - x[j]) +                      (y[i] - y[j]) * (y[i] - y[j]) +                      (z[i] - z[j]) * (z[i] - z[j]);         dist[i][j] = sqrt(dist[i][j]);       }     }     for (long long int i = 1; i <= n; i++) {       if (vis[i] == 0) {         long double big = 1e18 * 1.0;         long long int ans;         for (long long int j = i + 1; j <= n; j++) {           if (vis[j] == 0) {             if (dist[i][j] < big) {               big = dist[i][j];               ans = j;             }           }         }         vis[ans] = 1;         vis[i] = 1;         cout << i <<     << ans <<   n ;       }     }     return 0;   }   