It's been about two years since I last program c, now I need to do it for a basic project. How would I print out one letter in a string?

For example lets say I have a string called str=[Hello]. I want to display the third letter so just the "l".

Here's what I have so far

Code:
#include<stdio.h>
int main()
{
    char str[50] = "Hello";
    printf("The third letter is : %s \n",str[3]);
    return 0;
}