n=int(input())
if n>=90:
    print(n*3)
elif n>=80 and n<90:
    print(n*2)
elif n>=70 and n<80:
    print(n)
else:
    print(50)
/**************************************************************
	Problem: 1300
	User: admin
	Language: Python
	Result: Accepted
	Time:191 ms
	Memory:34244 kb
****************************************************************/