Community Dashboard

Special numbers

Practice

2.8 (33 votes)

Basic programming

Math

Number theory

Problem

89% Success 7576 Attempts 20 Points 1s Time Limit 256MB Memory 1024 KB Max Code

A natural number is special if it consists of only digits \(4\) and \(7\). Find the number of pairs of сoprime special numbers \((x,\ y)\) such that \(1 ⩽ x ⩽ y ⩽ N\).  Input format The first line contains an integer \(N\) (\(1 ⩽ N ⩽ 10^9\)). Output format Print a single number denoting the answer to the problem.

You need to be logged in to access the code editor

Please wait while we load the editor

Results

Custom Input

Run your code to see the output

Submissions

Please login to view your submissions