The function check_input(1, 3) will return 3. Here's why:\n1. Initially, x is 1 and y is 3. The first if condition (x < y) is true, so x becomes 2.\n2. The second if condition (x < y) is also true (2 < 3), so x becomes 3.\n3. The third if condition (x < y) is false (3 is not less than 3), so x remains 3.\n4. The function returns x, which is 3.