restructure zeta/** to storage/zeta/**

storage/zeta/cpp/completed/2738.cpp

@@ -0,0 +1,46 @@
+#include<iostream>
+#include<vector>
+
+using namespace std;
+
+auto sum(int N, int M, int A[], int B[], int S[]) {
+    for (int i = 0; i < N; i++) {
+        for (int j = 0; j < M; j++) {
+            S[i * M + j] = A[i * M + j] + B[i * M + j];
+        }
+    }
+    return S;
+}
+
+void display(int N, int M, int S[]) {
+    for (int i = 0; i < N; i++) {
+        for (int j = 0; j < M; j++) {
+            cout << S[i * M + j];
+            if (j < M - 1) {
+                cout << " ";
+            }
+        }
+        cout << endl;
+    }
+}
+
+int main() {
+    int N, M;
+    cin >> N >> M;
+    int A[N * M];
+    int B[N * M];
+    int S[N * M];
+    for (int i = 0; i < N; i++) {
+        for (int j = 0; j < M; j++) {
+            cin >> A[i * M + j];
+        }
+    }
+    for (int i = 0; i < N; i++) {
+        for (int j = 0; j < M; j++) {
+            cin >> B[i * M + j];
+        }
+    }
+    sum(N, M, A, B, S);
+    display(N, M, S);
+    return 0;
+}