What's wrong with this code?

[Chrys]

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

void swap_chars(char* str, int i, int j);

int main()
{
    char* s = "Hello World of C";
    
    printf("Before: %s\n", s);

    swap_chars(s, 0, 1);
    printf("After: %s\n", s);
    
    getchar();
}

void swap_chars(char* str, int i, int j)
{
    char t = str[i];
    
    str[i] = str[j];
    printf("here");
    str[j] = t;
}