请问哪里出问题了
#include<stdio.h>
#include<string.h>
int main()
{
char Strings[100001];
char letters[27] = { "abcdefghijklmnopqrstuvwxyz" };
gets_s(Strings);
int IfEqual = 0;
char TheLetter[27];
int Exist = 0;
for (int i = 0; i < 27; i++) {
for (int j = 0; Strings[j]!='\0'; j++) {
if (letters[i] == Strings[j]) {
IfEqual = 1;
break;
}
}
if (IfEqual == 0) {
Exist++;
TheLetter[Exist] = letters[i];
}
IfEqual = 0;
}
if (Exist == 0) {
printf("no");
}
else {
printf("%c\n", TheLetter[0]);
}
return 0;
}