#include<cstdio>
int main(){
    int n=0,jin=0,ma=0,ys=0;
    int l[12];
    for(int i=0;i<12;i++){scanf("%d",&l[i]);}
    if(l[0]>300){printf("%d",-1);return 0;}
    jin=300-l[0];
    for(int i=1;i<12;i++){if(jin+300<l[i]){printf("-%d",i+1);return 0;}
        ys+=300+jin-l[i];
        if(ys>100){
            jin=ys%100;
            ma=ys-jin;
        }
    }
    printf("%.2lf",ma*1.2+jin);return 0;
}