#include <stdio.h>

int main() {
    int experiment, expression, procedure, final;
    float grade;
    scanf("%d %d %d %d", &experiment, &expression, &procedure, &final);
    grade = experiment * 0.2 + expression * 0.1 + procedure * 0.2 + final * 0.5;
    printf("%.1f",grade);
    return 0;
}