关于文件和结构的内存无效引用呜呜呜？

#include<stdio.h>
struct pasw
{
	char input;
	char output;
}txt[100];
int main()
{	int i=0,z=0;
	char filename[15],mima[15],ch,c;
	scanf("%s",mima);
	scanf("%s",filename);
	FILE *fp1,*fp2;
	fp2 = fopen(mima,"r");
	fp1 = fopen(filename,"r");
	while((ch = fgetc(fp2))!=EOF)
	{	if(ch!=','&&z%2==0&&ch!='\n')
		{
			txt[i].input = ch;z++;
		}
		else if(ch!=','&&z%2==1&&ch!='\n')
		{
			txt[i].output = ch;z++;
			i++;
		}
	}
	z = sizeof(txt)/sizeof(struct pasw);
	ch++;
	while((ch = fgetc(fp1))!= EOF)
	{	for(i=0;ch!=txt[i].input&&i<=z;i++);
		if(i<z) printf("%c",txt[i].output);
		else printf("%c",ch);
	}
	fclose(fp1);
	fclose(fp2);
}