#include <stdio.h>
int ch;
int main()
{
    printf( "Please enter password: " );
again:
    ch = getchar();
    if ( ch == 'P' ) {
        printf( "password is correct, goodbye!" );
    } else {
        printf( "\rpassword is incorrect, please re-enter: " );
        goto again;
    }
    return 0;
}