chore: completed day_3 hard task

hard/day_3/.cph/.solution.cpp_c2f6d70d8f6905b229d78483cfc14d83.prob

@@ -0,0 +1 @@
+{"name":"Local: solution","url":"d:\\OPCODE\\Code\\codecrack\\hard\\day_3\\solution.cpp","tests":[{"id":1711262363902,"input":"8\n2 10 5 12 9 5 1 5","output":""}],"interactive":false,"memoryLimit":1024,"timeLimit":3000,"srcPath":"d:\\OPCODE\\Code\\codecrack\\hard\\day_3\\solution.cpp","group":"local","local":true}

hard/day_3/solution.cpp

@@ -1 +1,63 @@
-//Write your code here
+//Write your code here
+// HARE RAM HARE KRISHNA
+
+#include <bits/stdc++.h>
+using namespace std;
+#define int long long
+#define INF (int)1e18
+#define f first
+#define s second
+#define readyplayerone()                  \
+    {                                     \
+        ios_base::sync_with_stdio(false); \
+        cin.tie(0);                       \
+        cout.tie(0);                      \
+    }
+
+#define couty cout << "YES" << endl
+#define coutn cout << "NO" << endl
+#define cout(a) cout << a << endl
+
+#define min3(a, b, c) (a < b && a < c) ? a : (b < c) ? b \
+                                                     : c
+#define max3(a, b, c) (a > b && a > c) ? a : (b > c) ? b \
+                                                     : c
+
+#define fi(i, s, e) for (int i = s; i < e; i++)
+#define fd(i, s, e) for (int i = s; i > e; i--)
+
+#define ain(i, arr, n)          \
+    ;                           \
+    for (int i = 0; i < n; i++) \
+    {                           \
+        cin >> arr[i];          \
+    }
+#define aout(i, arr, n)         \
+    ;                           \
+    for (int i = 0; i < n; i++) \
+    {                           \
+        cout << arr[i] << "\t"; \
+    }
+
+int solve(int x){
+    int res = 0;
+    while(x){
+        x >>= 1;
+        res += x;
+    }
+    return res;
+}
+
+int32_t main(){
+    int n, k, x, res=0;
+    cin>>n;
+    k = solve(n-1);
+    for(int i = 0; i < n; i++){
+        cin>>x;
+        int a = solve(i);
+        int b = solve(n-i-1);
+        if(k - a - b == 0)
+            res ^= x;
+    }
+    cout(res);
+}