求两个字符串中第1个不相同的字符的ASCII码之差

#include<stdio.h>
#include<string.h>
#pragma warning(disable:4996)

int main()
{
    int i, j;
    char ch1[80], ch2[80];
    printf("请输入两个字符串：\n");
    scanf("%s", ch1);
    scanf("%s", ch2);
    i = strlen(ch1);
    j = strlen(ch2);
    for (i = 0, j = 0;; i++, j++)
    {
        if (ch1[i] != ch2[j])
        {
            printf("%d", ch1[i] - ch2[j]);
            break;
        }
    }
}