#include <cstdio>
#include <cmath>
 
int main() {
    double a;
    if (scanf("%lf", &a) != 1) return 0;
 
    double x = fmod(a, 1.5);      // (-1.5, 1.5)
    if (x < 0) x += 1.5;          // [0, 1.5)
 
    double ans = x * x * x - 2.25 * x;   // [0,1.5]-д үргэлж <= 0
 
    long long t = -(long long)floor(-ans * 10.0 + 1e-9);
 
    if (t == 0) {
        printf("0.0\n");
    } else {
        long long s = t < 0 ? -t : t;
        printf("%s%lld.%lld\n", t < 0 ? "-" : "", s / 10, s % 10);
    }
    return 0;
}

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