i keep getting the same number when i use my random number generator C++

i'm trying to make a random number generator in class this is what i have so far it gives me a random number on start up but once i tell the program to generate another one it gives me the same number.

 //computer guesses numbers betwen 1-100
#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;
int main() {
    srand(static_cast<unsigned int>(time(0))); // seeds the random number generator for the computer to ask if its the right number
    int computer_number = rand() % 100 + 1; //randomly selects a number betwen 1-100