#include <stdio.h>
 
int main() {
    int N, X, Y;
    printf("請輸入 N、X、Y (0 < Y): ");
    scanf("%d %d %d", &N, &X, &Y);
 
    int temperature = 20;  // 初始溫度為20攝氏度
 
    // 如果N是奇數，先把N減1，再“先加熱後冷卻”
    if (N % 2 == 1) {
        N -= 1;
        temperature += X; // 先加熱
    }
 
    // 使用循環計算最高溫度
    for (int i = 0; i < N / 2; i++) {
        // 先加熱
        temperature += X;
        // 再冷卻
        temperature -= Y;
        if (temperature < 20) {
            // 如果溫度低於室溫，設為室溫
            temperature = 20;
        }
    }
 
    printf("%d\n", temperature);
 
    return 0;
}
 

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