import std.stdio, std.math, std.conv, std.array, std.string, std.algorithm;

void main() {
    string str;
    while((str = readln()).length != 0) {
        double v = to!double(str.chomp);
        double t = (v/9.8)^^2 * 4.9;
        int nt = to!int(floor(to!real(t)));
        int h = nt + (5 - nt%5);
        writeln((h+5)/5);
    }
}