MathDB
pmo problem 5

Source: PMO 2021

March 20, 2021
algebranumber theoryPMO

Problem Statement

A positive integer is called \emph{lucky} if it is divisible by 77, and the sum of its digits is also divisible by 77. Fix a positive integer nn. Show that there exists some lucky integer ll such that nl70\left|n - l\right| \leq 70.