func_code_string: #include <bits/stdc++.h>   using namespace std;   bool debug = 1;   int n, m, k;   int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};   long long ln, lk, lm;   int a[100005];   int main() {     scanf( %d , &n);     for (int(i) = 0; (i) < (int)(n); (i)++) {       scanf( %d , a + i);     }     sort(a, a + n);     vector<int> vp;     for (int i = n - 1; i >= 1;) {       if (a[i] == a[i - 1] || a[i] - 1 == a[i - 1]) {         vp.push_back(a[i - 1]);         i -= 2;       } else         i--;     }     long long ans = 0;     for (int i = 0; i + 1 < vp.size(); i += 2) {       ans += (long long)vp[i] * vp[i + 1];     }     printf( %lld n , ans);   }   