#!/usr/bin/env python3

INPUT_FILE = 'input'

def main():
    content = list(map(str.strip, open(INPUT_FILE, 'r').readlines()))
    elfs = []
    cal_sum = 0
    for line in content:
        if line == '':
            elfs.append(cal_sum)
            cal_sum = 0
            continue
        cal_sum += int(line)
    print(max(elfs))

if __name__ == '__main__':
    main()