TLE三个点求助

#include<iostream>
#include<cstdio>
#include<cmath>
#include<queue>
#include<stack>
#include<set>
#include<bits/stdc++.h>
using namespace std;

int isprime(int t){
	if(t == 2) return 1; 
	else if(t == 1 || t % 2 == 0) return 0; 
	else if(t <= 0) return 0; 
	else{
	    int i = 3;
		while (i * i <= t){  
			if(t % i == 0){
				return 0;
			}
			else i ++;
		}
		return 1;
	}
}

int main(){
	int n , m , l , r;
	cin >> n >> m;
	for(int i = 1 ; i <= n ; i ++){
		cin >> l >> r;
		if(r > m || l > m || r < 1 || l < 1) {
			printf("Crossing the line\n");
			continue;
		}
		else{
			int cnt = 0;
			for(int j = l ; j <= r ; j ++){
				if(isprime(j)) cnt ++; 
			}
			printf("%d\n" , cnt);
		}
	}
	


	return 0;
}