C :

#include<stdio.h> 
int suShu(int x){
	int i,c=0;
	for(i = 2;i <= x / 2;i++){
		if(x % i == 0){
			c++;
			break;
		}
	}
	
	return c;
	
}

int suShuLiang(int m,int n){
	int i,c=0;
	for(i = m;i <= n;i++){
		if(i > 1){
			if(suShu(i) == 0){
				c++;
			}
		}
	}
	return c;	
}

int main(){ 
	int m,n;
	scanf("%d %d",&m,&n);
	printf("%d",suShuLiang(m,n));
	return 0;
} 

C++ :

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

int main(){
	int a,b,i,j,x=0,s=0;
	cin>>a>>b;
	for(i=a;i<=b;i++){
		x=0;
		for(j=2;j<=sqrt(i);j++){
			if(i%j==0){
				x++;
			}
		}
		if(x==0&&i!=1)
		s++;
	}cout<<s;
}

Python :

import math
n,m = map(int,input().split())
s = 0
for a in range (n,m+1):
    f = True;
    for i in range (2,int(math.sqrt(a))+1):
        if a % i ==0:
            f = False;
            break;
    if f == True and a != 1:
            s += 1
print(s)