pragma solidity ^0.4.24;

contract MyContract {
   struct Student {
       string studentName;
       string gender;
       uint age;
   }
   
   mapping(uint256 => Student) studentInfo;
   
   function setStudentInfo(uint _studentId, string _name, string _gender, uint _age) public {
       Student storage student = studentInfo[_studentId];
       
       student.studentName = _name;
       student.gender = _gender;
       student.age = _age;
   }
   
   function getStudentInfo(uint256 _studentId) public view returns (string, string, uint) {
       return (studentInfo[_studentId].studentName, studentInfo[_studentId].gender, studentInfo[_studentId].age);
   }
}