read Data from file in c compare

#include <iostream>
#include <cstdio>
#include <algorithm>
#define  MAX_SIZE 100
using namespace std;
struct  Activity{
    int id, start, finish;


}activities[MAX_SIZE];


bool comp(Activity a1, Activity a2){


    return  a1.finish<a2.finish;


}


int main() {
    freopen("input.txt","r",stdin);

    int  n;

    scanf("%d", &n);
    cout<<n<<endl;

    for (int i = 0; i <n ; i++) {

        scanf("%d%d%d", &activities[i].id, &activities[i].start, &activities[i].finish);

    }

    sort(activities,activities+n, comp);


    for (int i = 0; i <n ; i++) {

        printf("%d %d %d\n", activities[i].id,activities[i].start,activities[i].finish);

    }




    return 0;
}