gpa

#include <stdio.h>
int main(){
    double gpx = 0., hx = 0.;
    double g, h;
    while(~scanf("%lf%lf", &g, &h)){
        hx += h;
        if(g >= 60.){
            gpx += (4 - 3. * (100. - g) * (100. - g) / 1600.) * h;
        }
    }
    printf("%.2f\n", gpx / hx);
    return 0;
}