#include <stdio.h>
 
int main() {
    char x, y;
 
    if (x >= 'a' && x <= 'z') 
        x = x - 32;  // 小写转大写
    else 
        x = x + 32;  // 大写转小写
 
    if (y >= 'a' && y <= 'z') 
        y = y - 32;  
    else 
        y = y + 32;  
 
    return 0;
}
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