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

int max_of_four(int a, int b, int c, int d);
int greaterOfTwo(int a, int b);

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;
}
int max_of_four(int a, int b, int c, int d);
int greaterOfTwo(int a, int b);


int max_of_four(int a, int b, int c, int d)
{
    int max = 0;
    max = greaterOfTwo(a, b);
    max = greaterOfTwo(max, c);
    max = greaterOfTwo(max, d);
    return max;
}

int greaterOfTwo(int a, int b)
{
    return a > b ? a : b;
}