#include<stdio.h>
int M[2121][2121];
int main() {
int i, j, p, q;
for (i = 0; i < 3; i++) {
int x1, y1, x2, y2;
scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
for (p = x1; p < x2;p++){
for (q = y1; q < y2;q++){
M[p + 1000][q + 1000] = i<2?1:0;
}
}
}
int ans = 0;
for (i = 0; i < 2000; i++)for (j = 0; j < 2000; j++)ans += M[i][j];
printf("%d", ans);
return 0;
}
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