GFG FIRST DAY OF WEEK

#include <bits/stdc++.h>

using namespace std;
 
int dayofweek(int d, int m, int y) {
    static int t[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
    y -= m < 3;
    return ( y + y / 4 - y / 100 + y / 400 + t[m - 1] + d) % 7;
}

int main() {
    int day = dayofweek(30, 8, 2010);
    cout << day;
 
    return 0;
}