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import sys

def read_int_list():
    return list(map(int, [x for x in sys.stdin.readline().strip().split(' ') if x != '']))
    
if __name__=='__main__':
    n, m, s = read_int_list()
    Z = []
    for i in range(m):
        d, g = read_int_list()
        Z.append((d, g))
    Z.sort()
    T = []
    T.append(Z[0])
    for (d, g) in Z[1:]:
        if d == T[-1][1] + 1:
            T[-1] = (T[-1][0], g)
        else:
            T.append((d, g))
    p = None
    for (d, g) in T:
        if d > 1 and (p is None or abs(p-s) > abs(d-1-s)):
            p = d-1
        if g < n and (p is None or abs(p-s) > abs(g+1-s)):
            p = g+1
    print(p)