std::cin unexpected behaviour on large integer input

Question

cin unexpected behaviour on large integer input

When a large integer is provided as input, std::cin causes unexpected behaviour in the program.

std::cin unexpected behaviour when there is an integer overflow

#include <iostream>
int main() {

    int cpp_is_great;
    std::cin >> cpp_is_great;

    int just_an_integer;

    while(cpp_is_great > 0)
    {
        std::cin >> just_an_integer;
        std::cout << "magic of c++\n";

        cpp_is_great--;
    }

    return 0;
}

Output
10
1
magic of c++
10
magic of c++
10000000000000000000000000000000000000
magic of c++
magic of c++
magic of c++
magic of c++
magic of c++
magic of c++
magic of c++
magic of c++

scanf doesn't cause this issue, why?

This issue doesn't occur in scanf

#include <cstdio>

int main() {

    int c_is_really_great;
    scanf("%d",&c_is_really_great);

    int just_an_integer;

    while(c_is_really_great > 0)
    {
        scanf("%d",&just_an_integer);
        printf("no magic in c\n");

        c_is_really_great--;
    }

    return 0;
}

Output
10
1
no magic in c
10
no magic in c
10000000000000000000000000000000000000
no magic in c