During Problem Set i came across the error Expected Expression on the statement
    "string s = GetString();" Suggestions would be appreciated. The code is provided below.

        #include <cs50.h>
        #include <stdio.h>
        #include <string.h>
        #include <ctype.h>

        int main(void)
        {
            int s = 0; // Height
            int t = 0; // Line
            int u = 0; // Column
    
            do
            {
                // Gathers string.
                printf("Please provide the height of the pyramid: ");
                string s = GetString();
            }
            while (s < 1 || s > 23);

            // Selects a line.
            for (int t = 1; t <= s; t++)
            {
                // Selects a column.    
                for (int u = 1; u <= s; u++) 
                {
                // Prints character.
                if (u >= s + 1 - t)
                {
                    printf("#");
                }
                else
                {
                    printf(" ");
                }
                }
            }
            // Prints next line.
            printf("\n");
        }