/*
ID: fanzeyi1
LANG: C
TASK: carz 
*/
/*
 * =====================================================================================
 *
 *       Filename:  carz.c
 *        Version:  1.0
 *        Created:  11/09/2011 09:14:56 AM
 *       Revision:  none
 *       Compiler:  gcc
 *         Author:  Zeray Fan, fanzeyi1994[at]gmail.com
 *        Company:  http://www.fanhe.org/
 *
 * =====================================================================================
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 1001

double speed(int a) {
    if(a > 4) {
        return 7.0; 
    }else if(a > 3) {
        return 7.5; 
    }else if(a > 2) {
        return 8.0; 
    }else if(a > 1) {
        return 9.0; 
    }else{
        return 10.0; 
    }
}

inline double min(double a, double b) {
    return a < b ? a : b; 
}

int main(void) {
    FILE *fin = fopen("carz.in","r");
    FILE *fout = fopen("carz.out", "w");
    int i, j; 
    int s, t;
    double th; 
    double f[MAX]; 
    fscanf(fin, "%d %d\n", &s, &t); 
    s = s / 10; 
    th = t / 60.0; 
    memset(f, 0x7f, sizeof(f)); 
    f[0] = 0.000; 
    for( i = 1 ; i <= s ; i++ ) {
        for( j = 0 ; j < i ; j++ ) {
            if(j == 0) {
                f[i] = min(f[i], f[j] + (i - j) / speed(i - j)); 
            }else{
                f[i] = min(f[i], f[j] + (i - j) / speed(i - j) + th); 
            }
        }
    }
    fprintf(fout, "%.2lf\n", f[s]); 
    return 0;
}