
N, t = int(input()), int(input()) a = [] b = [] for i in range(N): ai, bi = map(int, input().split()) a.append(ai) b.append(bi) br = 0 for j in range(N): br += b[j] ar = 0 res = br + t for i in range(N): br -= b[i] ar += a[i] if ar + br + t < res: res = ar + br + t print(res)
n = int(input()) road = int(input()) a = 0 b = road for i in range(n): ai, bi = list(map(int, input().split())) a += ai b = min(b+bi, a+road) print(b)