import sys

sys.setrecursionlimit(10 ** 8)

input = sys.stdin.readline


def main():
    P, Q, R = [int(x) for x in input().split()]

    total = P + Q + R
    ans = max(P, Q, R) / total
    ans = max(ans, (P + Q) / total)
    ans = max(ans, (R + Q) / total)
    ans = max(ans, (R + P) / total)

    print(ans)

    
    

if __name__ == '__main__':
    main()