Untitled

#include <stdio.h>
int encrypt();
int decrypt();
int main(){
    int choice=0;
    while(choice == 0){
    printf("\nWhat would you like to do?\n");
    printf("1. Encrypt\n2. Decrypt\n3. Exit\n");
    printf("Option: ");
    scanf("%d", &choice);
    if (choice == 1)
        choice = encrypt();
    if (choice == 2)
        choice = decrypt();
    if (choice == 3)
        return 0;
    }
    return 0;
}
int encrypt(){
    char buffer[BUFSIZ];
    printf("\n\nInput: ");
    int i=0;
    char c;
    fflush(stdin);
    while((c=getchar()) !='\n'){
        buffer[i++] = c+13;
    }
    buffer[i] = '\0';
    FILE * Output;
    Output = fopen("encrypt.txt", "w+");
    fprintf(Output, buffer);
    fclose(Output);
    return 0;
}
int decrypt(){
    char buffer[BUFSIZ];
    int i=0;
    char c;
    FILE * Input;
    Input = fopen("encrypt.txt", "r");
    while((c=fgetc(Input))!=EOF){
        buffer[i++]= c - 13;
    }
    buffer[i] = '\0';
    printf("\n%s\n", buffer);
    fclose(Input);
    return 0;
}