m <- 10
n <- 10
mat <- matrix(sample(1:20L, m*n, replace=TRUE), nrow=m); mat
done <- FALSE
for(i in seq_len(m))
{
for(j in seq_len(n))
cat(mat[i,j])
if(mat[i,j] == 20)
done <- TRUE
break
}
cat(", ")
if(done)
cat("\n")