How do I do a C function that removes a character typed by the user from the phrase he typed? Unable to do the function

Question

//Ex: if the user type 'hello world' and type 'o' then the program must return the Mund, removing the letter the user typed.

#include <stdio.h>
#include <string.h>
int main(){
    char str[20],ch;
    int i, n, j;
    printf("Digite uma frase:\n");
    scanf("%s",str);
    printf("Digite uma letra dessa frase:\n");
    scanf("%c",&ch);
    n=strlen(str);

    for(i=0, j=0; i<n; i++)
    {
        if(str[i]!=ch)
        {
            str[j]=str[i];
            j++;
        }
    }
    str[j]='\0';
    printf("removemos a letra digitada: %s\n", str);
    return 0;
}