diff --git a/first-interpreter/src/execute.c b/first-interpreter/src/execute.c
index 9a3a722..fb0ece3 100644
--- a/first-interpreter/src/execute.c
+++ b/first-interpreter/src/execute.c
@@ -5,27 +5,16 @@
 #include "ast.h"
 
 typedef struct {
-    unsigned* i;
+    unsigned* next_free_cell_index;
     Array memory;
 } Memory;
 
-struct Cell {
-    char* name;
-    unsigned index;
-    struct Cell* next;
-};
-
-typedef struct {
-    struct Cell* next;
-} Scope;
-
 Memory new_memory() {
     unsigned size = 1024;
-    unsigned* i = (unsigned*)malloc(sizeof(unsigned));
-    *i = 0;
+    unsigned* next_free_cell_index = (unsigned*)calloc(1, sizeof(unsigned));
     int* mem = (int*)malloc(sizeof(int) * size);
     return (Memory){
-        .i = i,
+        .next_free_cell_index = next_free_cell_index,
         .memory = {
             .length = size,
             .elements = mem,
@@ -33,32 +22,43 @@ Memory new_memory() {
     };
 }
 
+struct Cell {
+    char* name;
+    int* memory_cell;
+    struct Cell* next;
+};
+
+typedef struct {
+    struct Cell* next;
+} Scope;
+
 Scope new_scope() {
     return (Scope) { .next = NULL };
 }
 
-int lookup_scope(char* name, Scope scope) {
+int* lookup(char* name, Scope scope) {
     struct Cell* cell = scope.next;
     while (cell != NULL) {
         if (strcmp(cell->name, name) == 0) {
-            return cell->index;
+            return cell->memory_cell;
         } else {
             cell = cell->next;
         }
     }
-    return -1;
+    return NULL;
 }
 
-Scope insert(char* name, int n, Memory memory, Scope scope) {
-    if (*memory.i + 1 < memory.memory.length) {
-        ((int*)(memory.memory.elements))[*memory.i] = n;
+Scope insert(char* name, int value, Memory memory, Scope scope) {
+    if (*memory.next_free_cell_index + 1 < memory.memory.length) {
+		int* memory_cell = &((int*)(memory.memory.elements))[*memory.next_free_cell_index];
+        ++*memory.next_free_cell_index;
+        *memory_cell = value;
         struct Cell* cell = (struct Cell*)malloc(sizeof(struct Cell));
         *cell = (struct Cell) {
             .name = name,
-            .index = *memory.i,
+            .memory_cell = memory_cell,
             .next = scope.next,
         };
-        ++*memory.i;
         Scope new_scope = (Scope) {.next = cell};
         return new_scope;
     }
@@ -66,24 +66,6 @@ Scope insert(char* name, int n, Memory memory, Scope scope) {
     exit(1);
 }
 
-int* lookup_mem(int index, Memory mem) {
-    if (index >= 0 && (unsigned)index < *(mem.i)) {
-        return &((int*)(mem.memory.elements))[index];
-    }
-    return NULL;
-}
-
-int* lookup(char* name, Memory memory, Scope scope) {
-    int index = lookup_scope(name, scope);
-    if (index >= 0) {
-        int* result = lookup_mem(index, memory);
-        if (result != NULL) {
-            return result;
-        }
-    }
-    return NULL;
-}
-
 int eval_expr(Expr expr, Memory memory, Scope scope) {
     switch (expr.tag) {
     default:
@@ -91,7 +73,7 @@ int eval_expr(Expr expr, Memory memory, Scope scope) {
         return expr.data.integer;
     }
     case VARIABLE: {
-        int* result = lookup(expr.data.variable, memory, scope);
+        int* result = lookup(expr.data.variable, scope);
         if (result == NULL) {
             fprintf(stderr, "Error: variable not found '%s'\n", expr.data.variable);
             exit(1);
@@ -138,7 +120,7 @@ Scope interpret_stmt(Stmt stmt, Memory memory, Scope scope) {
     switch (stmt.tag) {
     case SET: {
         int result = eval_expr(stmt.data.Set.expr, memory, scope);
-        int* index = lookup(stmt.data.Set.name, memory, scope);
+        int* index = lookup(stmt.data.Set.name, scope);
         if (index != NULL) {
             *index = result;
         } else {