X, Y ,D = map(int, input().split())

def Lpoint(x, y, d):
    if x + y < d:
        return 0
    else:
        if (d <= x and y < d) or (d <= y and x < d):
            return (d + 1) - (d - min(x, y))
        elif x < d and y < d:
            return (d + 1) - (d - x) - (d - y)
        else:
            return d + 1            

if __name__ == "__main__":    
    print(Lpoint(X, Y, D))