diff --git a/CMakeLists.txt b/CMakeLists.txt
index be9fbf8..79429ed 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,7 +19,6 @@ include_directories(include)
 add_library(calculator_lib
     src/lexer.c
     src/parser.c
-    src/ast.c
     src/evaluator.c
 )
 
diff --git a/include/ast.h b/include/ast.h
deleted file mode 100644
index e69de29..0000000
diff --git a/include/evaluator.h b/include/evaluator.h
index 8e1ea47..78c5730 100644
--- a/include/evaluator.h
+++ b/include/evaluator.h
@@ -4,6 +4,6 @@
 #include "lexer.h"
 #include <stdint.h>
 
-uint64_t evaluate(ASTNode *tree);
+int64_t evaluate(ASTNode *tree);
 
 #endif // !EVALUATOR_H
diff --git a/src/ast.c b/src/ast.c
deleted file mode 100644
index e69de29..0000000
diff --git a/src/evaluator.c b/src/evaluator.c
index fc0048d..cbaf776 100644
--- a/src/evaluator.c
+++ b/src/evaluator.c
@@ -2,17 +2,17 @@
 #include "lexer.h"
 #include <stdint.h>
 
-uint64_t evaluate(ASTNode *tree) {
+int64_t evaluate(ASTNode *tree) {
     if (tree->type == NODE_BINARY_OP) {
         switch (tree->data.binary.op) {
             case OP_ADD:
-                return evaluate(tree->data.binary.left) + evaluate(tree->data.binary.left);
+                return evaluate(tree->data.binary.left) + evaluate(tree->data.binary.right);
             case OP_SUB:
-                return evaluate(tree->data.binary.left) - evaluate(tree->data.binary.left);
+                return evaluate(tree->data.binary.left) - evaluate(tree->data.binary.right);
             case OP_MUL:
-                return evaluate(tree->data.binary.left) * evaluate(tree->data.binary.left);
+                return evaluate(tree->data.binary.left) * evaluate(tree->data.binary.right);
             case OP_DIV:
-                return evaluate(tree->data.binary.left) / evaluate(tree->data.binary.left);
+                return evaluate(tree->data.binary.left) / evaluate(tree->data.binary.right);
 
         }
     } else {
diff --git a/src/main.c b/src/main.c
index a18e12c..26053e9 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,16 +1,30 @@
+#include "evaluator.h"
 #include "lexer.h"
 #include "parser.h"
+#include <stdint.h>
+#include <inttypes.h>
 #include <stdlib.h>
 #include <stdio.h>
 
 int main(void) {
-    ASTNodeArray context;
+    char buf[256];
+    printf("Insert a valid mathematical expression: ");
+    
+    int c;
+    int pos = 0;
+    while ((c = getc(stdin)) != '\n' && c != EOF) {
+        buf[pos] = c;
+        pos++;
+    }
+    buf[pos] = '\0';
 
-    tokenize("3 + 4 * 5", &context);
+    ASTNodeArray context;
+    tokenize(buf, &context);
 
     AST tree = parse(&context);
+    int64_t result = evaluate(tree.head);
 
-    printf("Hola\n");
 
+    printf("El resultado es: %" PRIi64 "\n", result);
     return EXIT_SUCCESS;
 }
diff --git a/src/parser.c b/src/parser.c
index c348aac..c2ac315 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -17,7 +17,7 @@ uint8_t node_lbp(ASTNode node) {
             break;
         case OP_DIV:
         case OP_MUL:
-            return 30;
+            return 20;
         default:
             return 0;
     }
@@ -31,11 +31,13 @@ uint8_t node_rbp(ASTNode node) {
     switch (node.data.binary.op) {
         case OP_ADD:
         case OP_SUB:
-            return 20;
+            return 11;
             break;
         case OP_DIV:
         case OP_MUL:
-            return 40;
+            return 21;
+        default:
+            return 0;
     }
 }
 
@@ -51,7 +53,7 @@ bool ASTNodeSlice_is_valid(ASTNodeSlice *slice) {
     if (slice->arr->len < 1) {
         return false;
     }
-    if (slice->pos >= slice->arr->len - 1) {
+    if (slice->pos >= slice->arr->len) {
         return false;
     }
 
@@ -78,7 +80,7 @@ ASTNode *parse_expr(ASTNodeSlice *slice, uint8_t min_bp) {
             break;
         }
 
-        ASTNode operator = operator = ASTNodeSlice_peek(slice);
+        ASTNode operator = ASTNodeSlice_peek(slice);
         uint8_t rbp = node_rbp(operator);
         uint8_t lbp = node_lbp(operator);