diff --git a/main.c b/main.c
index 0655a91..484d9c5 100644
--- a/main.c
+++ b/main.c
@@ -1,11 +1,8 @@
 /*
 
-E ::= UT{+T}{-T}
-T ::= F{*F}{/F}
+E ::= T{+T}
+T ::= F{*F}
 F ::= (E)|i
-U ::= -|+|_
-
-'_' stands for empty sequence 
 
 */
 
@@ -15,199 +12,103 @@ U ::= -|+|_
 #include <stdbool.h>
 
 
-#define fatal(...) {\
-        fprintf(stderr, "\nError at char %d\n", number);\
-        fprintf(stderr, "%s\n", line);\
-        for (int i = 0; i < number - 1; i++)\
-            fputc(' ', stderr);\
-        fprintf(stderr, "^\nMessage: ");\
-        fprintf(stderr, __VA_ARGS__);\
-        exit(1);\
-    }
+#define eprintf(...) fprintf(stderr, __VA_ARGS__)
 
 
-typedef enum _NodeType {
-    NNUM = 1,
-    NOP = 2
-} NodeType;
+typedef enum TokenType {
+    INT,
+    PLUS,
+    MINUS,
+    LBRACE,
+    RBRACE
+} TokenType;
 
-typedef struct _Node Node;
-struct _Node {
-    Node *parent;
-    Node *left;
-    Node *right;
+typedef struct _Token {
+    TokenType type;
 
-    NodeType type;
+    int value;
+} Token;
 
-    int number;
-    char operator;  // + - * / m p
-};
 
-Node *e();
-Node *t();
-Node *f();
-Node *u();
-
-char line[1024];
-int symbol;
-int number = 0;
+void fatal(const char* message);
 void scan();
 
-int LRN(Node *node);
+void e();
+void t();
+void f();
+
+
+const int LINE_MAX = 1024;
+char *line;
+
+int symbol;
+int char_num = 0;
 
 
 int main(int argc, char* argv[]) {
-
-    memset(line, 0, 1024);
+    line = calloc(sizeof(char), LINE_MAX);
+    memset(line, 0, LINE_MAX);
 
     scan();
-    Node *root = e();
+    e();
 
     if (symbol != '\n') {
-        fatal("Syntax invalid\n");
+        fatal("Syntax invalid");
     }
 
     printf("Success\n");
-    printf("Answer: %d\n", LRN(root));
 
+    free(line);
     return 0;
 }
 
 void scan() {
     symbol = getchar();
     if (symbol == '\n')
-        line[number++] = ' ';
+        line[char_num++] = ' ';
     else
-        line[number++] = symbol;
+        line[char_num++] = symbol;
 }
 
-Node *e() {
-    Node *left, *right, *root;
-
-    root = u();
-    left = t();
-
-    if (root != NULL) {
-        root->left = left;
-        left = root;
-    }
-
-    while (symbol == '+' || symbol == '-') {
-        root = calloc(sizeof(Node), 1);
-        root->type = NOP;
-        root->operator = symbol;
-
+void e() {
+    t();
+    while (symbol == '+') {
         scan();
-        right = t();
-
-        root->left = left;
-        root->right = right;
-
-        left->parent = root;
-        right->parent = root;
-        left = root;
-        right = NULL;
+        t();
     }
-    return root;
 }
 
-Node *t() {
-    Node *left, *right, *root;
-    root = left = f();
-
-    while (symbol == '*' || symbol == '/') {
-        root = calloc(sizeof(Node), 1);
-        root->type = NOP;
-        root->operator = symbol;
-
+void t() {
+    f();
+    while (symbol == '*') {
         scan();
-        right = f();
-        
-        root->left = left;
-        root->right = right;
-
-        left->parent = root;
-        right->parent = root;
-        left = root;
-        right = NULL;
+        f();
     }
-    return root;
 }
 
-Node *f() {
-    Node *node;
+void f() {
     if (symbol == '(') {
         scan();
-        node = e();
+        e();
         if (symbol != ')') {
-            fatal("Expected parentheses, found '%c'\n", symbol);
+            fatal("Expected parentheses");
         }
     }
-    else if (symbol < '0' || symbol > '9') {
-        if (symbol == '\n') {
-            fatal("LF too early\n");
-        }
-        else {
-            fatal("Unexpected symbol '%c'\n", symbol);
-        }
+    else if (symbol >= '0' && symbol <= '9') {
+        ;
+    }
+    else if (symbol == '\n') {
+        fatal("LF too early");
     }
     else {
-        node = calloc(sizeof(Node), 1);
-        node->type = NNUM;
-        node->number = (int) (symbol - '0'); 
+        fatal("Unexpected symbol");
     }
     scan();
-    return node;
 }
 
-Node *u() {
-    if (symbol == '-' || symbol == '+') {
-        Node *node = calloc(sizeof(Node), 1);
-        node->type = NOP;
-        node->operator = (symbol == '+') ? 'p' : 'm';
-        scan();
-        return node;
-    }
-    return NULL;
-}
-
-int LRN(Node *node) {
-    int l, r, answer;
-
-    if (node == NULL)
-        return 0;
-
-    if (node->left != NULL)
-        l = LRN(node->left);
-
-    if (node->right != NULL)
-        r = LRN(node->right);
-
-    if (node->type == NOP) {
-        switch (node->operator) {
-        case '+':
-            answer = l + r; break;
-        case '-':
-            answer = l - r; break;
-        case '*':
-            answer = l * r; break;
-        case '/':
-            answer = l / r; break;
-        case 'm':
-            answer = -l; break;
-        case 'p':
-            answer = +l; break;
-        default:
-            fatal("Invalid operator indentifier: '%c'\n", node->operator); break;
-        }
-    }
-    else if (node->type == NNUM) {
-        answer = node->number;
-    }
-    else {
-        answer = 0;
-    }
-
-    free(node);
-    return answer;
+void fatal(const char* message) {
+    eprintf("\nError at char %d\n%s\n", char_num, line);
+    eprintf("%*c\n", char_num, '^');
+    eprintf("Message: %s\n", message);
+    exit(1);
 }