/*
ID: mytbk921
LANG: C
TASK: numtri
*/

#include <stdio.h>

int main()
{
	FILE *fin, *fout;
	int rows, tri[1000][1000];
	int i,j;

	fin = fopen("numtri.in", "r");
	fout = fopen("numtri.out", "w");

	fscanf(fin, "%d", &rows);

	for (i=0; i<rows; i++) {
		for (j=0; j<=i; j++)
			fscanf(fin, "%d", &tri[i][j]);
	}

	fclose(fin);

	for (i=rows-2; i>=0; i--) {
		for (j=0; j<=i; j++) {
			if (tri[i+1][j]>tri[i+1][j+1])
				tri[i][j] += tri[i+1][j];
			else
				tri[i][j] += tri[i+1][j+1];
		}
	}

	fprintf(fout, "%d\n", tri[0][0]);
	fclose(fout);
	return 0;
}