#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;
}

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