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#/bin/bash

r="$1"
a=0

for ((x=1;x<=r;x++)) {
    for ((y=0;y<r;y++)) {
        if ((x*x+y*y<=r*r));then
            a=$((a+1))
        else break
        fi
    }
}

z=$((a*4));m=$((z/(r*r)))
echo -n $m
z=$((z-m*r*r))
if ((z));then
    echo -n .
fi
for ((i=1;i<8&&z>0;i++)) {
    n=$((z*10/(r*r)))
    z=$((z*10-n*r*r))
    echo -n $n
}
echo