C :

#include<stdio.h>
int main()
{	
	
	int x;
	while(1==1){
		scanf("%d",&x);
		if(x!=0){
			int i,s=0;	
				for(i=2;i<=x;i++){
					int c=0;
					int n;
					for(n=2;n<=i/2;n++){
						if(i%n==0){
							c++;
							break;
						}
						
					}
					if(c==0){
							s++;
						}	
				}
				printf("%d ",s);
		}else{
			break;
		}
	
		
	}
	
	
	return 0;
	
}

C++ :

#include <bits/stdc++.h>
using namespace std;
int main()
{
	//c统计素数个数，f判断素数 
	int a[1100],n=0,c;
	bool f;
	while (1==1)
	{
		cin>>a[n];
		if (a[n]==0){
			break;
		}
		n++;
	}
	//i是下标 
	for (int i=0;i<n;i++)
	{
		c=0; 
		
		for(int j=2;j<=a[i];j++) 
		{
			f=true;
			for (int k=2;k<=sqrt(j);k++) 
			{
				if (j%k==0) 
				{
					f=false;
					break;
				}
			}
			if (f==true) c++;
		}
		cout<<c<<endl;
	}
	return 0;
}

Python :

import math
a = []
b = []
x = int(input())
while x != 0:
     a.append(x)
     x = int(input())
l = len(a)


for i in range(0,l):
     num = 0
     for j in range(1,a[i]+1):
          f = True
          for k in range(2,int(math.sqrt(j))+1):
               if j % k == 0:
                    f = False
                    break
          if j != 1 and f == True:
               num += 1
     b.append(num)

for l in b:
     print(l)