diff --git a/.travis.yml b/.travis.yml
index 884e3cd..e119fef 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -84,6 +84,10 @@ deploy:
   - <<: *deb
     dist: ubuntu/bionic
 
+  # 19.04
+  - <<: *deb
+    dist: ubuntu/disco
+
   # Fedora
   - <<: *rpm
     dist: fedora/24
diff --git a/Makefile b/Makefile
index f08a8c4..c8d03b7 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-VERSION := 9.0.2
+VERSION := 9.1.0
 MAJOR_VERSION := $(shell echo $(VERSION) | head -c 1)
 
 # installation directory (/usr/local by default)
diff --git a/docs/eprintf.3 b/docs/eprintf.3
deleted file mode 100644
index 0607b8f..0000000
--- a/docs/eprintf.3
+++ /dev/null
@@ -1,64 +0,0 @@
-'\" t
-.\"     Title: eprintf
-.\"    Author: [see the "AUTHOR(S)" section]
-.\" Generator: Asciidoctor 1.5.7.1
-.\"      Date: 2017-09-16
-.\"    Manual: CS50 Programmer's Manual
-.\"    Source: CS50
-.\"  Language: English
-.\"
-.TH "EPRINTF" "3" "2017-09-16" "CS50" "CS50 Programmer\(aqs Manual"
-.ie \n(.g .ds Aq \(aq
-.el       .ds Aq '
-.ss \n[.ss] 0
-.nh
-.ad l
-.de URL
-\fI\\$2\fP <\\$1>\\$3
-..
-.als MTO URL
-.if \n[.g] \{\
-.  mso www.tmac
-.  am URL
-.    ad l
-.  .
-.  am MTO
-.    ad l
-.  .
-.  LINKSTYLE blue R < >
-.\}
-.SH "NAME"
-eprintf \- prints an error message to stderr
-.SH "SYNOPSIS"
-.sp
-\fB#include <cs50.h>\fP
-.sp
-\fBvoid eprintf(const string format, ...);\fP
-.SH "DESCRIPTION"
-.sp
-Prints an error message formatted like \fBprintf(3)\fP to standard error, prefixing it with file and line number from which the function was called. See \fBprintf(3)\fP for more on formatting.
-.SH "EXAMPLE"
-.sp
-.if n .RS 4
-.nf
-int main(void)
-{
-    eprintf("This line of code should be executed\(rsn");
-
-    int i;
-    for (i = 0; i < 50; i++)
-    {
-        printf("i is %d\(rsn", i);
-    }
-
-    eprintf("Expected i to be 49 but it is actually %d\(rsn", i);
-}
-.fi
-.if n .RE
-.SH "SEE ALSO"
-.sp
-.if n .RS 4
-.nf
-printf(3)
-.fi
-.if n .RE
\ No newline at end of file
diff --git a/src/cs50.c b/src/cs50.c
index 5feac60..a51eec1 100644
--- a/src/cs50.c
+++ b/src/cs50.c
@@ -397,6 +397,43 @@ long get_long(const char *format, ...)
     }
 }
 
+/**
+ * Prompts user for a line of text from standard input and returns the
+ * equivalent long long; if text does not represent a long long in
+ * [-2^63, 2^63 - 1) or would cause underflow or overflow, user is
+ * prompted to retry. If line can't be read, returns LLONG_MAX.
+ */
+long long get_long_long(const string format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+
+    // Try to get a long long from user
+    while (true)
+    {
+        // Get line of text, returning LLONG_MAX on failure
+        string line = get_string(&ap, format);
+        if (line == NULL)
+        {
+            va_end(ap);
+            return LLONG_MAX;
+        }
+
+        // Return a long long if only a long long (in range) was provided
+        if (strlen(line) > 0 && !isspace((unsigned char) line[0]))
+        {
+            char *tail;
+            errno = 0;
+            long long n = strtoll(line, &tail, 10);
+            if (errno == 0 && *tail == '\0' && n < LLONG_MAX)
+            {
+                va_end(ap);
+                return n;
+            }
+        }
+    }
+}
+
 /**
  * Called automatically after execution exits main.
  */
diff --git a/src/cs50.h b/src/cs50.h
index 2b9d18b..b284ba2 100644
--- a/src/cs50.h
+++ b/src/cs50.h
@@ -94,6 +94,14 @@ int get_int(const char *format, ...) __attribute__((format(printf, 1, 2)));
  */
 long get_long(const char *format, ...) __attribute__((format(printf, 1, 2)));
 
+/**
+ * Prompts user for a line of text from standard input and returns the
+ * equivalent long long; if text does not represent a long long in
+ * [-2^63, 2^63 - 1) or would cause underflow or overflow, user is
+ * prompted to retry. If line can't be read, returns LLONG_MAX.
+ */
+long long get_long_long(const string format, ...) __attribute__((format(printf, 1, 2)));
+
 /**
  * Prompts user for a line of text from standard input and returns
  * it as a string (char *), sans trailing line ending. Supports