#include <stdio.h>

int max(int x, int y);

int main(void) {
    int a = 1, b = 5, c = 3, d = 4;

    printf("最大値は%dです\n", max(max(a, b), max(c, d)));

    return 0;
}

int max(int x, int y) {
    return (x > y) ? x : y;
}