easy problem，but you must make some changes
Var k,i:longint;
Begin
 readln(k);
 i:=3;
 while k mod i>0 do inc(i);
 writeln(i-1);
End.

Won't you get TLE?

Once upon a time people invented the game named Bashi. +1 for gyz113. It is realy very easy problem.

my solve-C++:

#include "iostream"
using namespace std;
int main()
{
    int K, L = 0, i;
    cin >> K;
    for (i = 2; i <= K; i++)
        if ((K % (i+1)) == 0)
        {
            cout << i;
            return 0;
        }
    cout << "0";
    return 0;
}

sorry for my English.