Ошибка после первого цикла

#include<iostream>
#include"stdio.h"
using namespace std;
typedef struct info{
char a[20],b[20];
int c,d;
}el;
int main(){
    el f[5];
    for(int i=0;i<5;i++){
        cout<<"Enter name of "<<i+1<<" person"<<endl;
        gets(f[i].a);
        cout<<"Enter lastname of "<<i+1<<" person"<<endl;
        gets(f[i].b);
        cout<<"Enter age of "<<i+1<<" person"<<endl;
        cin>>f[i].c;
        cout<<"Enter number of "<<i+1<<" person"<<endl;
        cin>>f[i].d;
    }
return 0;
}

cin.ignore(numeric_limits<int>::max(), '\n');

#include <iostream>
#include <limits>
#include <stdio.h>
using namespace std;
typedef struct info {
    char a[20], b[20];
    int c, d;
}el;
int main() {
    el f[5];
    for (int i = 0; i < 5; i++) {
        cout << "Enter name of " << i + 1 << " person" << endl;
        gets(f[i].a);
        cout << "Enter lastname of " << i + 1 << " person" << endl;
        gets(f[i].b);
        cout << "Enter age of " << i + 1 << " person" << endl;
        cin >> f[i].c;
        cout << "Enter number of " << i + 1 << " person" << endl;
        cin >> f[i].d;
        cin.ignore(numeric_limits<int>::max(), '\n');
    }
    return 0;
}

...
cin >> f[i].a;
...
cin >> f[i].b;
...