diff --git a/include/string/string.h b/include/string/string.h
index f01dbb9..382cda9 100644
--- a/include/string/string.h
+++ b/include/string/string.h
@@ -14,5 +14,6 @@ char *strcat(char *dest, const char *src);
 void strncpy(char* dst, const char* src, size_t n);
 int strncmp(const char* s1, const char* s2, size_t n);
 size_t strlen(const char* str);
+int atoi(const char* str);
 
 #endif
\ No newline at end of file
diff --git a/src/string/string.c b/src/string/string.c
index a42d0e6..5516b1d 100644
--- a/src/string/string.c
+++ b/src/string/string.c
@@ -71,7 +71,6 @@ void strncpy(char* dst, const char* src, size_t n)
    while(i++ != n && (*dst++ = *src++));
 }
 
-
 /*
  * strncmp - compare two strings up to n characters
  * @s1: first string
@@ -100,10 +99,36 @@ int strncmp(const char* s1, const char* s2, size_t n)
     }
 }
 
-// BSD implementation
+/*
+ * strlen - get length of a string (BSD implementation)
+ * @str: NULL-terminated string
+ * 
+ * Return:
+ * %len - length of string
+ */
 size_t strlen(const char* str)
 {
         const char* s;
         for (s = str; *s; ++s);
         return (s - str);
+}
+
+/*
+ * atoi - ascii to integer (PureDOOM implementation)
+ * @str: ASCII string to convert
+ *
+ * Return:
+ * %i - integer represented in @str
+ */
+int atoi(const char* str)
+{
+    int i = 0;
+    int c;
+
+    while ((c = *str++) != 0) {
+        i *= 10;
+        i += c - '0';
+    }
+
+    return i;
 }
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