N = int(input())
D = ""
for i in range(1,100):
    D += str(i)
D += "1"
K = len(D)
A = "0"*(500-K)+D
A = list(map(int,list(A)))
B = A[:]
co = 0
for _ in range(N-1):
    for k in range(-1,-501,-1):
        a = B[k]+A[k]+co
        co = a//10
        B[k] = a%10
x = B[-K:]
x = [str(x[i]) for i in range(K)]
x = "".join(x)
y = B[:500-K]
for _ in range(500-K):
    if y[0]==0:
        y.pop(0)
    else:break
if len(y)==0:
    y = "0"
else:
    y = [str(y[i]) for i in range(len(y))]
    y = "".join(y)
print(y+"."+x)