#include <stdio.h>
 
int main() {
    double a, b, c, d, x, max, min;
 
    printf("Enter a, b, c, d: ");
    scanf("%lf", &a);
    scanf("%lf", &b);
    scanf("%lf", &c);
    scanf("%lf", &d);
 
    // Находим максимум
    max = a;
    if (b > max) {
        max = b;
    }
    if (c > max) {
        max = c;
    }
    if (d > max) {
        max = d;
    }
 
    // Находим минимум
    min = a + c;
    if ((b - d) < min) {
        min = b - d;
    }
 
    // Вычисляем результат
    x = max + min;
 
    printf("x = %.4f\n", x);
    return 0;
}

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