#include <iostream>
#include <cstdio>
using namespace std;

/*
Add `int max_of_four(int a, int b, int c, int d)` here.
*/
int max_of_four(int a, int b, int c, int d) {
    if(a>b && b<c && c<d)
        return a;
    else if(b>a && a<c && c<d)
        return b;
     else if(c>a && a<b && b<d)
        return c;
     else
        return d;

}

int main() {
    int a, b, c, d;
    scanf("%d %d %d %d", &a, &b, &c, &d);
    int ans = max_of_four(a, b, c, d);
    printf("%d", ans);

    return 0;
}

what's wrong in this code? it is showing that

solution.cc: In function 'int main()':
solution.cc:22:41: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d %d %d", &a, &b, &c, &d);

[Edit by moderator]: Reformatted code segment.