796 B | 796 chars
import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
h, w, n = mii()
l = [mii() for _ in range(n)]
d = [[0] * w for _ in range(h)]
for i in range(n):
y, x, ey, ex = l[i]
for k in range(y - 1, ey):
d[k][x - 1] = i + 1
d[k][ex - 1] = i + 1
for k in range(x - 1, ex):
d[y - 1][k] = i + 1
d[ey - 1][k] = i + 1
for i in d:
for j in i:
if j == 0:
print(end=".")
else:
print(end=chr(96+j))
print()
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
solve()