#include<stdio.h>
int Max(int a, int b, int c) {
    int max = a;
    if (max < b)
        max = b;
    if (max < c)
        max = c;
    return max;
}


int main() {
    int a, b, c;
    float m = 0.0;
    scanf("%d %d %d", &a, &b, &c);
    int ret = Max(a + b, b, c);
    int ret2 = Max(a, b + c, c);
    int ret3 = Max(a, b, b + c);
    m = (float) ret / (ret2 + ret3);
    printf("%.2f", m);
    return 0;
}