#include <stdio.h>
#include <string.h>
#include <ctype.h>
 
#define MAX_WORD_LEN 128
#define MAX_ABBR_LEN 128
 
// 判斷這個單字是否需要略過
int is_skip_word(const char *word) {
    return strcmp(word, "of") == 0 ||
           strcmp(word, "and") == 0 ||
           strcmp(word, "the") == 0 ||
           strcmp(word, "at") == 0;
}
 
int main() {
    char word[MAX_WORD_LEN];
    char abbrs[1000][MAX_ABBR_LEN]; // 存所有縮寫，最多 1000 組
    int abbr_count = 0;
    char current_abbr[MAX_ABBR_LEN];
    int current_len = 0;
 
    // 不斷從輸入中讀單字
    while (scanf("%s", word) != EOF) {
        int len = strlen(word);
        int is_last_word = 0;
 
        // 如果最後一個字元是句號
        if (word[len - 1] == '.') {
            is_last_word = 1;
            word[len - 1] = '\0'; // 去掉句號方便處理
        }
 
        if (!is_skip_word(word)) {
            current_abbr[current_len++] = toupper(word[0]);
        }
 
        if (is_last_word) {
            current_abbr[current_len] = '\0'; // 結束縮寫字串
            strcpy(abbrs[abbr_count++], current_abbr); // 存到縮寫列表
            current_len = 0; // 重設下一組縮寫
        }
    }
 
    // 輸出所有縮寫，用空白隔開
    for (int i = 0; i < abbr_count; ++i) {
        if (i > 0) printf(" ");
        printf("%s", abbrs[i]);
    }
    printf("\n");
 
    return 0;
}
 

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the civil works administration. file transfer protocol. chief executive
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united states geological survey. crime scene investigation.