N = int(input())

P = [1] + [0] + [1] * (N - 1)

for i in range(2, N + 1):
    
    if P[i]:
        
        for j in range(2 * i, N + 1, i):
            
            P[j] = 0
            
print(sum([i for i in range(N + 1) if P[i]]))