number=7.0
primes=3
divisor=3
while (primes<1000):
    if ((number%divisor)>0):
        while (divisor<(number/2)):
            if ((number%divisor)>0):
                divisor=divisor+2
            else:
                primes=primes-1
                divisor=100
        primes=primes+1
        number=number+2
        divisor=3
    else:
        number=number+2
if (primes==1000):
    number=number-2
else:
    number=number
print number