import std.stdio, std.string, std.algorithm, std.range, std.conv, std.typecons, std.math;
void main(){
    auto x = readln.chomp.to!ulong;
    auto n = x / 11 * 2;
    auto m = x % 11;
    if (1 <= m && m <= 6) {
        n++;
    } else if (7 <= m) {
        n += 2;
    }
    writeln(n);
}